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Document and Entity Information - USD ($) $ in Billions	12 Months Ended
Document and Entity Information - USD ($) $ in Billions	Sep. 30, 2017	Nov. 03, 2017	Mar. 31, 2017
Document and Entity Information
Entity Registrant Name	AECOM
Entity Central Index Key	0000868857
Document Type	10-K
Document Period End Date	Sep. 30, 2017
Amendment Flag	false
Current Fiscal Year End Date	--09-30
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 5.3
Entity Common Stock, Shares Outstanding		157,624,270
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
CURRENT ASSETS:
Cash and cash equivalents	$ 665,871	$ 588,644
Cash in consolidated joint ventures	136,491	103,501
Total cash and cash equivalents	802,362	692,145
Accounts receivable-net	5,127,743	4,531,460
Prepaid expenses and other current assets	696,718	730,101
Income taxes receivable	55,399	47,065
TOTAL CURRENT ASSETS	6,682,222	6,000,771
PROPERTY AND EQUIPMENT-NET	621,357	644,992
DEFERRED TAX ASSETS-NET	171,331	171,508
INVESTMENTS IN UNCONSOLIDATED JOINT VENTURES	364,223	330,485
GOODWILL	5,992,881	5,823,843
INTANGIBLE ASSETS-NET	415,096	479,439
OTHER NON-CURRENT ASSETS	149,846	218,898
TOTAL ASSETS	14,396,956	13,669,936
CURRENT LIABILITIES:
Short-term debt	1,221	26,303
Accounts payable	2,249,872	1,910,915
Accrued expenses and other current liabilities	2,245,519	2,384,815
Income taxes payable	38,176	10,774
Billings in excess of costs on uncompleted contracts	902,812	631,928
Current portion of long-term debt	140,779	340,021
TOTAL CURRENT LIABILITIES	5,578,379	5,304,756
OTHER LONG-TERM LIABILITIES	322,199	403,364
DEFERRED TAX LIABILITY-NET	20,515	13,097
PENSION BENEFIT OBLIGATIONS	559,068	694,073
LONG-TERM DEBT	3,702,109	3,702,157
TOTAL LIABILITIES	10,182,270	10,117,447
COMMITMENTS AND CONTINGENCIES (Note 18)
AECOM STOCKHOLDERS' EQUITY:
Common stock-authorized, 300,000,000 shares of $0.01 par value as of September 30, 2017 and 2016; issued and outstanding 157,529,419 and 153,901,500 shares as of September 30, 2017 and 2016, respectively	1,575	1,539
Additional paid-in capital	3,733,572	3,604,519
Accumulated other comprehensive loss	(700,661)	(857,582)
Retained earnings	961,640	618,445
TOTAL AECOM STOCKHOLDERS' EQUITY	3,996,126	3,366,921
Noncontrolling interests	218,560	185,568
TOTAL STOCKHOLDERS' EQUITY	4,214,686	3,552,489
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 14,396,956	$ 13,669,936

Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2017	Sep. 30, 2016
Consolidated Balance Sheets
Common stock, authorized shares	300,000,000	300,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, issued shares	157,529,419	153,901,500
Common stock, outstanding shares	157,529,419	153,901,500

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Consolidated Statements of Operations
Revenue	$ 4,856,400	$ 4,561,500	$ 4,427,200	$ 4,358,300	$ 4,323,100	$ 4,408,800	$ 4,381,200	$ 4,297,700	$ 18,203,402	$ 17,410,825	$ 17,989,880
Cost of revenue	4,686,300	4,386,300	4,258,800	4,188,300	4,175,900	4,237,500	4,197,800	4,156,800	17,519,682	16,768,001	17,454,692
Gross profit	170,100	175,200	168,400	170,000	147,200	171,300	183,400	140,900	683,720	642,824	535,188
Equity in earnings of joint ventures	31,900	66,500	21,800	21,400	21,200	18,500	39,100	25,200	141,582	104,032	106,245
General and administrative expenses	(36,900)	(34,000)	(29,900)	(32,600)	(28,200)	(28,700)	(29,500)	(28,700)	(133,309)	(115,088)	(113,975)
Acquisition and integration expenses	(3,300)		(20,000)	(15,400)	(71,200)	(50,700)	(50,700)	(41,000)	(38,709)	(213,642)	(398,440)
Gain (loss) on disposal activities			600				(1,600)	(41,000)	572	(42,589)
Income from operations	161,800	207,700	140,900	143,400	69,000	110,400	140,700	55,400	653,856	375,537	129,018
Other income	2,500	2,100	1,300	800	2,900	1,500	800	3,000	6,636	8,180	19,139
Interest expense	(54,300)	(61,600)	(61,800)	(53,600)	(73,300)	(62,600)	(62,700)	(59,500)	(231,310)	(258,162)	(299,627)
Income (loss) before income tax (benefit) expense	110,000	148,200	80,400	90,600	(1,400)	49,300	78,800	(1,100)	429,182	125,555	(151,470)
Income tax expense (benefit)	6,200	12,100	(35,400)	24,800	(14,300)	(35,100)	12,200	(700)	7,706	(37,917)	(80,237)
Net income (loss)	103,800	136,100	115,800	65,800	12,900	84,400	66,600	(400)	421,476	163,472	(71,233)
Noncontrolling interests in income of consolidated subsidiaries, net of tax	(15,300)	(34,800)	(13,400)	(18,600)	(5,700)	(17,000)	(24,700)	(20,000)	(82,086)	(67,363)	(83,612)
Net income (loss) attributable to AECOM	$ 88,500	$ 101,300	$ 102,400	$ 47,200	$ 7,200	$ 67,400	$ 41,900	$ (20,400)	$ 339,390	$ 96,109	$ (154,845)
Net income (loss) attributable to AECOM per share:
Basic (in dollars per share)	$ 0.56	$ 0.65	$ 0.66	$ 0.31	$ 0.05	$ 0.44	$ 0.27	$ (0.13)	$ 2.18	$ 0.62	$ (1.04)
Diluted (in dollars per share)	$ 0.55	$ 0.64	$ 0.65	$ 0.30	$ 0.05	$ 0.43	$ 0.27	$ (0.13)	$ 2.13	$ 0.62	$ (1.04)
Weighted average shares outstanding:
Basic (in shares)	157,500	155,800	155,400	154,300	156,300	154,900	154,300	153,600	155,728	154,772	149,605
Diluted (in shares)	161,100	158,800	158,700	158,000	157,900	156,200	155,400	153,600	159,135	156,073	149,605

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Consolidated Statements of Comprehensive Income (Loss)
Net income (loss)	$ 103,800	$ 136,100	$ 115,800	$ 65,800	$ 12,900	$ 84,400	$ 66,600	$ (400)	$ 421,476	$ 163,472	$ (71,233)
Other comprehensive income (loss), net of tax:
Net unrealized gain (loss) on derivatives, net of tax									4,605	5,987	(9,196)
Foreign currency translation adjustments									65,389	(65,224)	(285,520)
Pension adjustments, net of tax									87,061	(164,911)	12,953
Other comprehensive income (loss), net of tax									157,055	(224,148)	(281,763)
Comprehensive income (loss), net of tax									578,531	(60,676)	(352,996)
Noncontrolling interests in comprehensive income of consolidated subsidiaries, net of tax									(82,220)	(65,697)	(80,347)
Comprehensive income (loss) attributable to AECOM, net of tax									$ 496,311	$ (126,373)	$ (433,343)

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total AECOM Stockholders' Equity	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Retained Earnings	Non-Controlling Interests	Total
BALANCE at Sep. 30, 2014	$ 2,186,517	$ 967	$ 1,864,971	$ (356,602)	$ 677,181	$ 85,963	$ 2,272,480
Increase (Decrease) in Stockholders' Equity
Net income (loss)	(154,845)				(154,845)	83,612	(71,233)
Other comprehensive income (loss)	(278,498)			(278,498)		(3,265)	(281,763)
Issuance of stock	1,577,981	525	1,577,456				1,577,981
Repurchases of stock	(23,113)	16	(23,129)				(23,113)
Proceeds from exercise of options	11,073	5	11,068				11,073
Tax benefit from exercise of stock options	2,781		2,781				2,781
Stock based compensation	85,852		85,852				85,852
Other noncontrolling interests						201,154	201,154
Contributions from noncontrolling interests						133	133
Distributions to noncontrolling interests						(144,402)	(144,402)
BALANCE at Sep. 30, 2015	3,407,748	1,513	3,518,999	(635,100)	522,336	223,195	3,630,943
Increase (Decrease) in Stockholders' Equity
Net income (loss)	96,109				96,109	67,363	163,472
Other comprehensive income (loss)	(222,482)			(222,482)		(1,666)	(224,148)
Issuance of stock	28,086	21	28,065				28,086
Repurchases of stock	(25,892)	1	(25,893)				(25,892)
Proceeds from exercise of options	9,946	4	9,942				9,946
Stock based compensation	73,406		73,406				73,406
Other noncontrolling interests						(155)	(155)
Contributions from noncontrolling interests						2,006	2,006
Distributions to noncontrolling interests						(105,175)	(105,175)
BALANCE at Sep. 30, 2016	3,366,921	1,539	3,604,519	(857,582)	618,445	185,568	3,552,489
Increase (Decrease) in Stockholders' Equity
Net income (loss)	339,390				339,390	82,086	421,476
Cumulative effect of accounting standard adoption	3,805				3,805		3,805
Other comprehensive income (loss)	156,921			156,921		134	157,055
Issuance of stock	66,665	41	66,624				66,665
Repurchases of stock	(25,078)	(7)	(25,071)				(25,078)
Proceeds from exercise of options	4,878	2	4,876				4,878
Stock based compensation	83,774		83,774				83,774
Acquisition of noncontrolling interests	(1,150)		(1,150)				(1,150)
Other noncontrolling interests						9,808	9,808
Contributions from noncontrolling interests						2,282	2,282
Distributions to noncontrolling interests						(61,318)	(61,318)
BALANCE at Sep. 30, 2017	$ 3,996,126	$ 1,575	$ 3,733,572	$ (700,661)	$ 961,640	$ 218,560	$ 4,214,686

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 421,476	$ 163,472	$ (71,233)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	278,631	398,730	599,265
Equity in earnings of unconsolidated joint ventures	(141,582)	(104,032)	(106,245)
Distribution of earnings from unconsolidated joint ventures	137,031	149,215	157,616
Non-cash stock compensation	83,774	73,406	85,852
Prepayment penalty on unsecured senior notes			55,639
Excess tax benefit from share-based payment			(3,642)
Foreign currency translation	6,007	(25,494)	(19,632)
Write-off of debt issuance costs		7,749	8,997
Deferred income tax benefit	(49,856)	(110,122)	(53,034)
Pension curtailment and settlement gains		(7,818)
(Gain) loss on disposal activities	(572)	42,589
Other	(15,062)	2,430	(18,248)
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(432,769)	337,291	369,600
Prepaid expenses and other assets	(21,780)	(16,257)	7,988
Accounts payable	292,496	16,616	142,126
Accrued expenses and other current liabilities	(53,126)	(154,096)	(118,488)
Billings in excess of costs on uncompleted contracts	234,116	(22,949)	(128,371)
Other long-term liabilities	(68,714)	53,411	(143,757)
Income taxes payable	26,584	10,014
Net cash provided by operating activities	696,654	814,155	764,433
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments for business acquisitions, net of cash acquired	(103,075)	(5,534)	(3,293,284)
Proceeds from disposal of businesses, net of cash disposed	2,200	39,699	15,127
Investment in unconsolidated joint ventures	(59,684)	(76,707)	(44,761)
Return of investment in unconsolidated joint ventures	35,407	5,160	12,056
Proceeds from sales of investments	900	11,745	126,370
Payments for purchase of investments		(214)	(91,810)
Proceeds from disposal of property and equipment	7,895	54,622	44,906
Payments for capital expenditures	(86,354)	(191,386)	(114,332)
Net cash used in investing activities	(202,711)	(162,615)	(3,345,728)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from borrowings under credit agreements	5,953,249	4,706,225	6,581,703
Repayments of borrowings under credit agreements	(7,071,602)	(5,199,961)	(5,158,254)
Proceeds from issuance of unsecured senior notes	1,000,000		1,600,000
Redemption of unsecured senior notes	(179,208)
Prepayment penalty on unsecured senior notes			(55,639)
Cash paid for debt and equity issuance costs	(13,041)	(10,447)	(89,567)
Proceeds from issuance of common stock	30,093	28,192	25,561
Proceeds from exercise of stock options	4,878	9,946	11,073
Payments to repurchase common stock	(25,078)	(25,892)	(23,113)
Excess tax benefit from share-based payment			3,642
Net distributions to noncontrolling interests	(59,036)	(103,169)	(144,269)
Other financing activities	(26,745)	(42,873)	(31,373)
Net cash (used in) provided by financing activities	(386,490)	(637,979)	2,719,764
EFFECT OF EXCHANGE RATE CHANGES ON CASH	2,764	(5,309)	(28,764)
NET INCREASE IN CASH AND CASH EQUIVALENTS	110,217	8,252	109,705
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	692,145	683,893	574,188
CASH AND CASH EQUIVALENTS AT END OF YEAR	802,362	692,145	683,893
SUPPLEMENTAL CASH FLOW INFORMATION:
Common stock issued in acquisitions	36,611		1,554,912
Debt assumed from acquisitions	31,353	1,805	567,657
Interest paid	226,090	216,125	179,939
Net income (taxes paid) tax refunds received	$ (11,540)	$ (13,109)	$ 27,349

Significant Accounting Policies

12 Months Ended

Sep. 30, 2017

Significant Accounting Policies

Significant Accounting Policies

1. Significant Accounting Policies

Organization—AECOM and its consolidated subsidiaries design, build, finance and operate infrastructure assets for governments, businesses and organizations around the world. The Company provides planning, consulting, architectural and engineering design services to commercial and government clients worldwide in major end markets such as transportation, facilities, environmental, energy, water and government. The Company also provides construction services, including building construction and energy, infrastructure and industrial construction, primarily in the Americas. In addition, the Company provides program and facilities management and maintenance, training, logistics, consulting, technical assistance, and systems integration and information technology services, primarily for agencies of the U.S. government and also for national governments around the world.

Fiscal Year—The Company reports results of operations based on 52 or 53-week periods ending on the Friday nearest September 30. For clarity of presentation, all periods are presented as if the year ended on September 30. Fiscal years 2017, 2016 and 2015 each contained 52 weeks and ended on September 29, September 30, and October 2, respectively.

Use of Estimates—The preparation of financial statements in conformity with accounting principles generally accepted in the United States (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The more significant estimates affecting amounts reported in the consolidated financial statements relate to revenues under long-term contracts and self-insurance accruals. Actual results could differ from those estimates.

Principles of Consolidation and Presentation—The consolidated financial statements include the accounts of all majority-owned subsidiaries and joint ventures in which the Company is the primary beneficiary. All inter-company accounts have been eliminated in consolidation. Also see Note 6 regarding joint ventures and variable interest entities.

Revenue Recognition—The Company generally utilizes a cost-to-cost approach in applying the percentage-of-completion method of revenue recognition. Under this approach, revenue is earned in proportion to total costs incurred, divided by total costs expected to be incurred. Recognition of revenue and profit is dependent upon a number of factors, including the accuracy of a variety of estimates made at the balance sheet date, engineering progress, material quantities, the achievement of milestones, penalty provisions, labor productivity and cost estimates made at the balance sheet date. Due to uncertainties inherent in the estimation process, actual completion costs may vary from estimates. If estimated total costs on contracts indicate a loss, the Company recognizes that estimated loss within cost of revenues in the period the estimated loss first becomes known. Liabilities recorded related to accrued contract losses were not material as of September 30, 2017 and 2016.

In the course of providing its services, the Company routinely subcontracts for services and incurs other direct costs on behalf of its clients. These costs are passed through to clients and, in accordance with industry practice and GAAP, are included in the Company's revenue and cost of revenue. Because subcontractor services and other direct costs can change significantly from project to project and period to period, changes in revenue may not be indicative of business trends. These subcontractor and other direct costs for the years ended September 30, 2017, 2016 and 2015 were $9.2 billion, $8.4 billion and $8.3 billion, respectively.

Cost-Reimbursable Contracts

Cost-reimbursable contracts consists of two similar contract types: (1) cost-plus contracts and (2) time-and-materials price contracts.

Cost-Plus Contracts. The Company enters into two major types of cost-plus contracts:

Cost-Plus Fixed Fee. Under cost-plus fixed fee contracts, the Company charges clients for its costs, including both direct and indirect costs, plus a fixed negotiated fee. The total estimated cost plus the fixed negotiated fee represents the total contract value. The Company recognizes revenue based on the actual labor and other direct costs incurred, plus the portion of the fixed fee it has earned to date.

Cost-Plus Fixed Rate. Under the Company's cost-plus fixed rate contracts, the Company charges clients for its direct and indirect costs based upon a negotiated rate. The Company recognizes revenue based on the actual total costs it has expended and the applicable fixed rate.

Certain cost-plus contracts provide for award fees or a penalty based on performance criteria in lieu of a fixed fee or fixed rate. Other contracts include a base fee component plus a performance-based award fee. In addition, the Company may share award fees with subcontractors. The Company records accruals for fee-sharing as fees are earned. The Company generally recognizes revenue to the extent of costs actually incurred plus a proportionate amount of the fee expected to be earned. The Company takes the award fee or penalty on contracts into consideration when estimating revenue and profit rates, and it records revenue related to the award fees when there is sufficient information to assess anticipated contract performance. On contracts that represent higher than normal risk or technical difficulty, the Company may defer all award fees until an award fee letter is received. Once an award fee letter is received, the estimated or accrued fees are adjusted to the actual award amount.

Certain cost-plus contracts provide for incentive fees based on performance against contractual milestones. The amount of the incentive fees varies, depending on whether the Company achieves above, at, or below target results. The Company originally recognizes revenue on these contracts based upon expected results. These estimates are revised when necessary based upon additional information that becomes available as the contract progresses.

Time-and-Materials Price Contracts

Time-and-Materials Price Contracts. Under time-and-materials contracts, the Company negotiates hourly billing rates and charges its clients based on the actual time that it expends on a project. In addition, clients reimburse the Company for its actual out-of-pocket costs of materials and other direct incidental expenditures that it incurs in connection with its performance under the contract. Profit margins on time-and-materials contracts fluctuate based on actual labor and overhead costs that it directly charges or allocates to contracts compared to negotiated billing rates. Many of the Company's time-and-materials contracts are subject to maximum contract values and, accordingly, revenue relating to these contracts is recognized as if these contracts were a fixed-price contract.

Guaranteed Maximum Price Contracts

Guaranteed Maximum Price. Guaranteed maximum price contracts (GMP) are common for design-build and commercial and residential projects. GMP contracts share many of the same contract provisions as cost-plus and fixed-price contracts. A contractor performing work pursuant to a cost-plus, GMP or fixed-price contract will all enter into trade contracts directly. Both cost-plus and GMP contracts generally include an agreed lump sum or percentage fee which is called out and separately identified and the contracts are considered 'open' book providing the owner with full disclosure of the project costs. A fixed-price contract provides the owner with a single lump sum amount without specifically identifying the breakdown of fee or costs and is typically 'closed' book thereby providing the owner with little detail as to the project costs. In a GMP contract, unlike the cost-plus contract, the Company provides the owner with a guaranteed price for the overall construction (adjusted for change orders issued by the owner) and with a schedule which includes a completion date for the project. In addition, cost overruns in a GMP contract would generally be the Company's responsibility and in the event the Company's actions or inactions result in delays to the project, the Company may be responsible to the owner for costs associated with such delay. For many of the Company's commercial and residential GMP contracts, the final price is generally not established until the Company have awarded a substantial percentage of the trade contracts and it has negotiated additional contractual limitations, such as mutual waivers of consequential damages as well as aggregate caps on liabilities and liquidated damages.

Fixed-Price Contracts

Fixed-Price. Fixed-price contracting is the predominant contracting method outside of the United States. There are typically two types of fixed-price contracts. The first and more common type, lump-sum, involves performing all of the work under the contract for a specified lump-sum fee. Lump-sum contracts are typically subject to price adjustments if the scope of the project changes or unforeseen conditions arise. The second type, fixed-unit price, involves performing an estimated number of units of work at an agreed price per unit, with the total payment under the contract determined by the actual number of units delivered. The Company recognizes revenue on fixed-price contracts using the percentage-of-completion method described above. Prior to completion, recognized profit margins on any fixed-price contract depend on the accuracy of the Company's estimates and will increase to the extent that its actual costs are below the estimated amounts. Conversely, if the Company's costs exceed these estimates, its profit margins will decrease and the Company may realize a loss on a project. The Company recognizes anticipated losses on contracts in the period in which they become evident.

During the years ended September 30, 2017, 2016 and 2015, the types of contracts comprising the Company's revenue were as follows:

	Fiscal Year Ended
	September 30, 2017			September 30, 2016			September 30, 2015
Cost reimbursable		48	%		53	%		57	%
Guaranteed maximum price		23	%		15	%		15	%
Fixed price		29	%		32	%		28	%

Cost reimbursable contracts include cost-plus and time-and-materials price contracts.

Contract Claims—Claims are amounts in excess of the agreed contract price (or amounts not included in the original contract price) that the Company seeks to collect from customers or others for delays, errors in specifications and designs, contract terminations, change orders in dispute or unapproved as to both scope and price or other causes of unanticipated additional costs. The Company records contract revenue related to claims only if it is probable that the claim will result in additional contract revenue and if the amount can be reliably estimated. In such cases, the Company records revenue only to the extent that contract costs relating to the claim have been incurred. As of September 30, 2017 and 2016, aggregate receivables related to contract claims were not significant to the overall receivable position of the Company and represented less than 5% of net receivables.

Government Contract Matters—The Company's federal government and certain state and local agency contracts are subject to, among other regulations, regulations issued under the Federal Acquisition Regulations (FAR). These regulations can limit the recovery of certain specified indirect costs on contracts and subjects the Company to ongoing multiple audits by government agencies such as the Defense Contract Audit Agency (DCAA). In addition, most of the Company's federal and state and local contracts are subject to termination at the discretion of the client.

Audits by the DCAA and other agencies consist of reviews of the Company's overhead rates, operating systems and cost proposals to ensure that the Company accounted for such costs in accordance with the Cost Accounting Standards of the FAR (CAS). If the DCAA determines the Company has not accounted for such costs consistent with CAS, the DCAA may disallow these costs. There can be no assurance that audits by the DCAA or other governmental agencies will not result in material cost disallowances in the future.

Cash and Cash Equivalents—The Company's cash equivalents include highly liquid investments which have an initial maturity of three months or less.

Allowance for Doubtful Accounts—The Company records its accounts receivable net of an allowance for doubtful accounts. This allowance for doubtful accounts is estimated based on management's evaluation of the contracts involved and the financial condition of its clients. The factors the Company considers in its contract evaluations include, but are not limited to:

•Client type—federal or state and local government or commercial client;

•Historical contract performance;

•Historical collection and delinquency trends;

•Client credit worthiness; and

•General economic conditions.

Derivative Financial Instruments—The Company accounts for its derivative instruments as either assets or liabilities and carries them at fair value.

For derivative instruments that hedge the exposure to variability in expected future cash flows that are designated as cash flow hedges, the effective portion of the gain or loss on the derivative instrument is reported as a component of accumulated other comprehensive income in stockholders' equity and reclassified into income in the same period or periods during which the hedged transaction affects earnings. The ineffective portion of the gain or loss on the derivative instrument, if any, is recognized in current income. To receive hedge accounting treatment, cash flow hedges must be highly effective in offsetting changes to expected future cash flows on hedged transactions.

The net gain or loss on the effective portion of a derivative instrument that is designated as an economic hedge of the foreign currency translation exposure generated by the re-measurement of certain assets and liabilities denominated in a non-functional currency in a foreign operation is reported in the same manner as a foreign currency translation adjustment. Accordingly, any gains or losses related to these derivative instruments are recognized in current income.

Derivatives that do not qualify as hedges are adjusted to fair value through current income.

Fair Value of Financial Instruments—The Company determines the fair values of its financial instruments, including short-term investments, debt instruments and derivative instruments, and pension and post-retirement plan assets based on inputs or assumptions that market participants would use in pricing an asset or a liability. The Company categorizes its instruments using a valuation hierarchy for disclosure of the inputs used to measure fair value. This hierarchy prioritizes the inputs into three broad levels as follows: Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities; Level 2 inputs are quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability, either directly or indirectly through market corroboration, for substantially the full term of the financial instrument; Level 3 inputs are unobservable inputs based on the Company's assumptions used to measure assets and liabilities at fair value. The classification of a financial asset or liability within the hierarchy is determined based on the lowest level input that is significant to the fair value measurement.

The carrying amounts of cash and cash equivalents, accounts receivable and accounts payable approximate fair value because of the short maturities of these instruments. The carrying amount of the revolving credit facility approximates fair value because the interest rates are based upon variable reference rates.

The Company's fair value measurement methods may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. Although the Company believes its valuation methods are appropriate and consistent with those used by other market participants, the use of different methodologies or assumptions to determine fair value could result in a different fair value measurement at the reporting date.

Property and Equipment—Property and equipment are recorded at cost and are depreciated over their estimated useful lives using the straight-line method. Expenditures for maintenance and repairs are expensed as incurred. Typically, estimated useful lives range from ten to forty-five years for buildings, three to ten years for furniture and fixtures and three to twelve years for computer systems and equipment. Leasehold improvements are amortized on a straight-line basis over the shorter of their estimated useful lives or the remaining terms of the underlying lease agreement.

Long-lived Assets—Long-lived assets to be held and used are reviewed for impairment whenever events or circumstances indicate that the assets may not be recoverable. The carrying amount of an asset to be held and used is not recoverable if it exceeds the sum of the undiscounted cash flows expected from the use and eventual disposition of the asset. For assets to be held and used, impairment losses are recognized based upon the excess of the asset's carrying amount over the fair value of the asset. For long-lived assets to be disposed, impairment losses are recognized at the lower of the carrying amount or fair value less cost to sell.

Goodwill and Acquired Intangible Assets—Goodwill represents the excess of amounts paid over the fair value of net assets acquired from an acquisition. In order to determine the amount of goodwill resulting from an acquisition, the Company performs an assessment to determine the value of the acquired company's tangible and identifiable intangible assets and liabilities. In its assessment, the Company determines whether identifiable intangible assets exist, which typically include backlog and customer relationships. Intangible assets are amortized over the period in which the contractual or economic benefits of the intangible assets are expected to be realized.

The Company tests goodwill for impairment annually for each reporting unit in the fourth quarter of the fiscal year and between annual tests, if events occur or circumstances change which suggest that goodwill should be evaluated. Such events or circumstances include significant changes in legal factors and business climate, recent losses at a reporting unit, and industry trends, among other factors. A reporting unit is defined as an operating segment or one level below an operating segment. The Company's impairment tests are performed at the operating segment level as they represent the Company's reporting units.

The impairment test is a two-step process. During the first step, the Company estimates the fair value of the reporting unit using income and market approaches, and compares that amount to the carrying value of that reporting unit. In the event the fair value of the reporting unit is determined to be less than the carrying value, a second step is required. The second step requires the Company to perform a hypothetical purchase allocation for that reporting unit and to compare the resulting current implied fair value of the goodwill to the current carrying value of the goodwill for that reporting unit. In the event that the current implied fair value of the goodwill is less than the carrying value, an impairment charge is recognized. See also Note 3.

Pension Plans—The Company has certain defined benefit pension plans. The Company calculates the market-related value of assets, which is used to determine the return-on-assets component of annual pension expense and the cumulative net unrecognized gain or loss subject to amortization. This calculation reflects the Company's anticipated long-term rate of return and amortization of the difference between the actual return (including capital, dividends, and interest) and the expected return over a five-year period. Cumulative net unrecognized gains or losses that exceed 10% of the greater of the projected benefit obligation or the market related value of plan assets are subject to amortization.

Insurance Reserves—The Company maintains insurance for certain insurable business risks. Insurance coverage contains various retention and deductible amounts for which the Company accrues a liability based upon reported claims and an actuarially determined estimated liability for certain claims incurred but not reported. It is generally the Company's policy not to accrue for any potential legal expense to be incurred in defending the Company's position. The Company believes that its accruals for estimated liabilities associated with professional and other liabilities are sufficient and any excess liability beyond the accrual is not expected to have a material adverse effect on the Company's results of operations or financial position.

Foreign Currency Translation—The Company's functional currency is generally the U.S. dollar, except for foreign operations where the functional currency is generally the local currency. Results of operations for foreign entities are translated to U.S. dollars using the average exchange rates during the period. Assets and liabilities for foreign entities are translated using the exchange rates in effect as of the date of the balance sheet. Resulting translation adjustments are recorded as a foreign currency translation adjustment into other accumulated comprehensive income/(loss) in stockholders' equity.

The Company uses foreign currency forward contracts from time to time to mitigate foreign currency risk. The Company limits exposure to foreign currency fluctuations in most of its contracts through provisions that require client payments in currencies corresponding to the currency in which costs are incurred. As a result of this natural hedge, the Company generally does not need to hedge foreign currency cash flows for contract work performed.

Noncontrolling Interests—Noncontrolling interests represent the equity investments of the minority owners in the Company's joint ventures and other subsidiary entities that the Company consolidates in its financial statements.

Income Taxes—The Company files a consolidated U.S. federal corporate income tax return and combined / consolidated state tax returns and separate company state tax returns. The Company accounts for certain income and expense items differently for financial reporting and income tax purposes. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax basis of assets and liabilities, applying enacted statutory tax rates in effect for the year in which the differences are expected to reverse. In determining the need for a valuation allowance, management reviews both positive and negative evidence, including the nature, frequency, and severity of cumulative financial reporting losses in recent years, the future reversal of existing temporary differences, predictability of future taxable income exclusive of reversing temporary differences of the character necessary to realize the asset, relevant carryforward periods, taxable income in carry-back years if carry-back is permitted under tax law, and prudent and feasible tax planning strategies that would be implemented, if necessary, to protect against the loss of the deferred tax asset that would otherwise expire. Based upon management's assessment of all available evidence, the Company has concluded that it is more likely than not that the deferred tax assets, net of valuation allowance, will be realized.

New Accounting Pronouncements and Changes in Accounting	12 Months Ended
New Accounting Pronouncements and Changes in Accounting	Sep. 30, 2017
New Accounting Pronouncements and Changes in Accounting
New Accounting Pronouncements and Changes in Accounting	2. New Accounting Pronouncements and Changes in Accounting In May 2014, the Financial Accounting Standards Board (FASB) issued new accounting guidance which amended the existing accounting standards for revenue recognition. The new accounting guidance establishes principles for recognizing revenue upon the transfer of promised goods or services to customers, in an amount that reflects the expected consideration received in exchange for those goods or services. The amendments may be applied retrospectively to each prior period presented or retrospectively with the cumulative effect recognized as of the date of initial application. The Company continues to evaluate the impact of the new guidance on its consolidated financial statements, including the expected impact on our business processes, systems, and controls, and potential differences in the timing or method of revenue recognition for its contracts. The Company expects to adopt the new standard on October 1, 2018, using the modified retrospective method that may result in a cumulative effect adjustment as of the date of adoption. In February 2015, the FASB issued amended guidance to the consolidation standard which updates the analysis that a reporting entity must perform to determine whether it should consolidate certain types of legal entities. The amendment modifies the evaluation of whether limited partnerships and similar legal entities are variable interest entities (VIEs) or voting interest entities and affects the consolidation analysis of reporting entities that are involved with VIEs, particularly those that have fee arrangements and related party relationships, among other provisions. This amended guidance was effective for the Company's fiscal year beginning October 1, 2016. The adoption of this guidance did not have a material impact on the Company's financial statements. In April 2015, the FASB issued new accounting guidance which requires debt issuance costs to be presented in the balance sheet as a direct deduction from the carrying value of the associated debt liability, consistent with the presentation of a debt discount. Prior to the issuance of the standard, debt issuance costs were required to be presented in the balance sheet as an asset. The guidance requires retrospective application and represents a change in accounting principle. This guidance was effective for the Company's fiscal year beginning October 1, 2016, which resulted in the reclassifications of $52.3 million and $56.8 million of unamortized debt issuance costs at September 30, 2017 and September 30, 2016, respectively, from other non-current assets to long-term debt. In April 2015, the FASB issued new accounting guidance which provides the use of a practical expedient that permits the entity to measure defined benefit plans assets and obligations using the month-end date that is closest to the entity's fiscal year-end date and apply that practical expedient consistently from year to year. This guidance was effective for the Company's fiscal year beginning October 1, 2016 and did not have a material impact on its consolidated financial statements. In February 2016, the FASB issued new accounting guidance which changes accounting requirements for leases. The new guidance requires lessees to recognize the assets and liabilities arising from all leases, including those classified as operating leases under previous accounting guidance, on the balance sheet. It also requires disclosure of key information about leasing arrangements to increase transparency and comparability among organizations. The new guidance will be effective for the Company's fiscal year beginning October 1, 2019 with early adoption permitted. The new guidance must be adopted using a modified retrospective transition approach and provides for certain practical expedients. The Company is currently evaluating the impact that the new guidance will have on its consolidated financial statements. In March 2016, the FASB issued new accounting guidance which simplifies the accounting for employee share-based payments. The new guidance requires all income tax effects of awards to be recognized in the statement of operations when the awards vest or are settled. It also allows an employer to repurchase more of an employee's shares for tax withholding purposes without triggering liability accounting and to make a policy election to account for forfeitures as they occur. The Company elected early adoption of this standard beginning October 1, 2016. The adoption of this guidance did not have a material impact on the Company's consolidated financial statements. In June 2016, the FASB issued a new credit loss standard that changes the impairment model for most financial assets and certain other instruments. The new guidance will replace the current "incurred loss" approach with an "expected loss" model for instruments measured at amortized cost. It also simplifies the accounting model for purchased credit-impaired debt securities and loans. The guidance will be effective for the Company's fiscal year starting October 1, 2020. The Company is currently evaluating the impact that the new guidance will have on its consolidated financial statements. In August 2016, the FASB issued new accounting guidance clarifying how entities should classify certain cash receipts and cash payments on the statement of cash flows. The new guidance also clarifies how the predominance principle should be applied when cash receipts and cash payments have aspects of more than one class of cash flows. The new guidance will be effective for the Company in its fiscal year beginning October 1, 2018, and early adoption is permitted. The Company is currently evaluating the impact that the new guidance will have on its consolidated statement of cash flows. In January 2017, the FASB issued new accounting guidance to simplify the test for goodwill impairment. This guidance eliminates step two from the goodwill impairment test. Under the new guidance, an entity should recognize an impairment charge for the amount by which the carrying amount of a reporting unit exceeds its fair value. However, the loss recognized should not exceed the total amount of goodwill allocated to the reporting unit. This guidance is effective for the Company in the first quarter of fiscal 2021, and earlier adoption is permitted. The Company is currently evaluating the impact that this guidance will have on its consolidated financial statements.

- Definition

The entire disclosure for reporting accounting changes and error corrections. It includes the conveyance of information necessary for a user of the Company's financial information to understand all aspects and required disclosure information concerning all changes and error corrections reported in the Company's financial statements for the period.

+ References + Details

Business Acquisitions, Goodwill and Intangible Assets

12 Months Ended

Sep. 30, 2017

Business Acquisitions, Goodwill and Intangible Assets

Business Acquisitions, Goodwill and Intangible Assets

3. Business Acquisitions, Goodwill, and Intangible Assets

On October 17, 2014, the Company completed the acquisition of the U.S. headquartered URS Corporation (URS), an international provider of engineering, construction, and technical services, by purchasing 100% of the outstanding shares of URS common stock. The Company paid total consideration of approximately $2.3 billion in cash and issued approximately $1.6 billion of AECOM common stock to the former stockholders and certain equity award holders of URS. In connection with the acquisition, the Company also assumed URS's senior notes totaling $0.4 billion, net of Company repayments. The Company repaid in full URS's $0.6 billion 2011 term loan and $0.1 billion of URS's revolving line of credit.

The Company acquired backlog and customer relationship intangible assets valued at $973.8 million representing the fair value of existing contracts and the underlying customer relationships, that have lives ranging from 1 to 11 years (weighted average lives of approximately 3 years) in connection with the URS acquisition. Acquired accrued expenses and other current liabilities include URS project liabilities and approximately $240 million related to estimated URS legal settlements and uninsured legal damages; see Note 18, Commitments and Contingencies, including legal matters related to former URS affiliates.

Amortization of intangible assets relating to URS, included in cost of revenue, was $83.6 million and $183.3 million during the twelve months ended September 30, 2017 and 2016, respectively. Additionally, included in equity in earnings of joint ventures and noncontrolling interests was intangible amortization expense of $9.4 million and $(8.5) million, respectively, during the twelve months ended September 30, 2017 and $23.0 million and $(13.8) million, respectively, during the twelve months ended September 30, 2016 related to joint venture fair value adjustments.

Billings in excess of costs on uncompleted contracts includes a margin fair value liability associated with long-term contracts acquired in connection with the acquisition of URS. This margin fair value liability was $149.1 million at the acquisition date, and its carrying value was $8.6 million at September 30, 2017, and is recognized as revenue on a percentage-of-completion basis as the applicable projects progress. The majority of this liability was recognized over the first two years from the acquisition date. Revenue and the related income from operations related to the margin fair value liability recognized during the twelve months ended September 30, 2017 and 2016 was $6.3 million and $37.2 million, respectively.

Acquisition and integration expenses, relating to business acquisitions, in the accompanying consolidated statements of operations are comprised of the following:

	Fiscal Year Ended
	Sept 30, 2017		Sept 30, 2016
	(in millions)
Severance and personnel costs	$	32.0	$	23.4
Professional service, real estate-related, and other expenses		6.7		190.2

Total	$	38.7	$	213.6

Included in severance and personnel costs for the twelve months ended September 30, 2017 and 2016 was $9.8 million and $21.8 million of severance expenses, respectively, of which $6.9 million and $19.3 million was paid as of September 30, 2017 and 2016, respectively. All acquisition and integration expenses are classified within Corporate, as presented in Note 19.

In addition to URS, the Company completed two, one and one business acquisitions during the years ended September 30, 2017, 2016 and 2015, respectively. These other business acquisitions did not meet the quantitative thresholds to require separate disclosures based on the Company's consolidated assets, investments and net income.

Business acquisitions during the year ended September 30, 2017 included Shimmick Construction Company, Inc. (Shimmick), a leading heavy civil construction firm in California and the Western U.S. for consideration of $165.5 million.

Excluding URS, the aggregate value of all consideration for acquisitions consummated during the years ended September 30, 2017, 2016 and 2015 were $166.6 million, $5.5 million and $27.3 million, respectively. The following table summarizes the estimated fair values of the assets acquired and liabilities assumed, as of the acquisition dates, from acquisitions consummated during the fiscal year presented:

	Fiscal Year Ended Sept 30, 2017
	(in millions)
Cash acquired	$	28.0
Other current assets		118.3
Identifiable intangible assets:
Customer relationships, contracts and backlog		24.5
Trademark / tradename		1.8

Total intangible assets	$	26.3

Goodwill		127.1
Other non-current assets		29.5
Current liabilities		(123.1	)
Non-current liabilities		(29.3	)
Noncontrolling interest		(10.2	)

Net assets acquired	$	166.6

Consideration for acquisitions above includes the following:

	Fiscal Year Ended Sept 30, 2017
	(in millions)
Cash paid	$	130.0
Equity issued		36.6

Total consideration	$	166.6

All of the above acquisitions were accounted for under the purchase method of accounting. As such, the purchase consideration of each acquired company was allocated to acquired tangible and intangible assets and liabilities based upon their fair values. The excess of the purchase consideration over the fair value of the net tangible and identifiable intangible assets acquired was recorded as goodwill. The determination of fair values of assets and liabilities acquired requires the Company to make estimates and use valuation techniques when market value is not readily available. The results of operations of each company acquired have been included in the Company's financial statements from the date of acquisition. Transaction costs associated with business acquisitions are expensed as they are incurred.

At the time of acquisition, the Company preliminarily estimates the amount of the identifiable intangible assets acquired based upon historical valuations of similar acquisitions and the facts and circumstances available at the time. The Company determines the final value of the identifiable intangible assets as soon as information is available, but not more than 12 months from the date of acquisition. The initial accounting for the Shimmick acquisition is not complete as of September 30, 2017. Post-acquisition adjustments primarily relate to project related liabilities.

Loss on disposal activities of $42.6 million in the accompanying statements of operations for the twelve months ended September 30, 2016 included losses on the disposition of non-core energy related businesses, equipment and other assets acquired with URS and reported within the Construction Services segment. Net assets related to the loss on disposal activities were $112.8 million at the date of disposal. Income from operations included losses incurred by non-core businesses of $9.4 million and $36.9 million during the twelve months ended September 30, 2017 and 2016, respectively.

The changes in the carrying value of goodwill by reportable segment for the fiscal years ended September 30, 2017 and 2016 were as follows:

	Fiscal Year 2017
	September 30, 2016		Acquisitions		Disposed			Foreign Exchange Impact		September 30, 2017
	(in millions)
Design and Consulting Services	$	3,198.2	$	3.8	$	(1.8	)	$	18.7	$	3,218.9
Construction Services		915.2		123.3		—			11.4		1,049.9
Management Services		1,710.4		—		—			13.7		1,724.1

Total	$	5,823.8	$	127.1	$	(1.8	)	$	43.8	$	5,992.9

	Fiscal Year 2016
	September 30, 2015		Post- Acquisition Adjustments		Disposed			Foreign Exchange Impact			September 30, 2016
	(in millions)
Design and Consulting Services	$	3,163.3	$	26.7	$	—		$	8.2		$	3,198.2
Construction Services		918.5		8.7		(11.3	)		(0.7	)		915.2
Management Services		1,738.9		4.0		—			(32.5	)		1,710.4

Total	$	5,820.7	$	39.4	$	(11.3	)	$	(25.0	)	$	5,823.8

The gross amounts and accumulated amortization of the Company's acquired identifiable intangible assets with finite useful lives as of September 30, 2017 and 2016, included in intangible assets—net, in the accompanying consolidated balance sheets, were as follows:

	September 30, 2017							September 30, 2016
	Gross Amount		Accumulated Amortization			Intangible Assets, Net		Gross Amount		Accumulated Amortization			Intangible Assets, Net		Amortization Period (years)
	(in millions)
Backlog and customer relationships	$	1,283.6	$	(870.2	)	$	413.4	$	1,247.1	$	(767.7	)	$	479.4	1 - 11
Trademark / tradename		18.3		(16.6	)		1.7		16.4		(16.4	)		—	0.3 - 2

Total	$	1,301.9	$	(886.8	)	$	415.1	$	1,263.5	$	(784.1	)	$	479.4

Amortization expense of acquired intangible assets included within cost of revenue was $102.7 million, $202.4 million, and $391.0 million for the years ended September 30, 2017, 2016 and 2015, respectively. The following table presents estimated amortization expense of existing intangible assets for the succeeding years:

Fiscal Year	(in millions)
2018	$	91.7
2019		84.5
2020		70.5
2021		59.5
2022		46.3
Thereafter		62.6

Total	$	415.1

Accounts Receivable - Net

12 Months Ended

Sep. 30, 2017

Accounts Receivable - Net

Accounts Receivable - Net

4. Accounts Receivable—Net

Net accounts receivable consisted of the following:

	Fiscal Year Ended
	September 30, 2017			September 30, 2016
	(in millions)
Billed	$	2,317.8		$	2,267.6
Unbilled		2,293.5			1,890.2
Contract retentions		568.6			434.1

Total accounts receivable—gross		5,179.9			4,591.9
Allowance for doubtful accounts		(52.2	)		(60.4	)

Total accounts receivable—net	$	5,127.7		$	4,531.5

Billed accounts receivable represent amounts billed to clients that have yet to be collected. Unbilled accounts receivable represents the contract revenue recognized but not yet billed pursuant to contract terms or accounts billed after the period end. Substantially all unbilled receivables as of September 30, 2017 and 2016 are expected to be billed and collected within twelve months. Contract retentions represent amounts invoiced to clients where payments have been withheld pending the completion of certain milestones, other contractual conditions or upon the completion of the project. These retention agreements vary from project to project and could be outstanding for several months or years.

Allowances for doubtful accounts have been determined through specific identification of amounts considered to be uncollectible and potential write-offs, plus a non-specific allowance for other amounts for which some potential loss has been determined to be probable based on current and past experience.

Other than the U.S. government, no single client accounted for more than 10% of the Company's outstanding receivables at September 30, 2017 and 2016.

The Company sold trade receivables to financial institutions, of which $325.2 million and $356.3 million were outstanding as of September 30, 2017 and 2016, respectively. The Company does not retain financial or legal obligations for these receivables that would result in material losses. The Company's ongoing involvement is limited to the remittance of customer payments to the financial institutions with respect to the sold trade receivables.

- Definition

The entire disclosure for claims held for amounts due a entity, excluding financing receivables. Examples include, but are not limited to, trade accounts receivables, notes receivables, loans receivables. Includes disclosure for allowance for credit losses.

+ References + Details

Property and Equipment

12 Months Ended

Sep. 30, 2017

Property and Equipment

Property and Equipment

5. Property and Equipment

Property and equipment, at cost, consists of the following:

	Fiscal Year Ended
	September 30, 2017			September 30, 2016			Useful Lives (years)
	(in millions)
Building and land	$	63.6		$	57.9		10 - 45
Leasehold improvements		404.6			381.4		1 - 20
Computer systems and equipment		694.6			652.0		3 - 12
Furniture and fixtures		135.9			129.7		3 - 10

Total		1,298.7			1,221.0
Accumulated depreciation and amortization		(677.3	)		(576.0	)

Property and equipment, net	$	621.4		$	645.0

Depreciation expense for the fiscal years ended September 30, 2017, 2016 and 2015 were $157.1 million, $171.7 million, and $191.3 million, respectively. Depreciation is calculated using primarily the straight-line method over the estimated useful lives of the assets, or in the case of leasehold improvements and capitalized leases, the lesser of the remaining term of the lease or its estimated useful life.

Joint Ventures and Variable Interest Entities

12 Months Ended

Sep. 30, 2017

Joint Ventures and Variable Interest Entities

Joint Ventures and Variable Interest Entities

6. Joint Ventures and Variable Interest Entities

The Company's joint ventures provide architecture, engineering, program management, construction management, operations and maintenance services and invests in real estate, public-private partnership (P3) and infrastructure projects. Joint ventures, the combination of two or more partners, are generally formed for a specific project. Management of the joint venture is typically controlled by a joint venture executive committee, comprised of representatives from the joint venture partners. The joint venture executive committee normally provides management oversight and controls decisions which could have a significant impact on the joint venture.

Some of the Company's joint ventures have no employees and minimal operating expenses. For these joint ventures, the Company's employees perform work for the joint venture, which is then billed to a third-party customer by the joint venture. These joint ventures function as pass through entities to bill the third-party customer. For consolidated joint ventures of this type, the Company records the entire amount of the services performed and the costs associated with these services, including the services provided by the other joint venture partners, in the Company's result of operations. For certain of these joint ventures where a fee is added by an unconsolidated joint venture to client billings, the Company's portion of that fee is recorded in equity in earnings of joint ventures.

The Company also has joint ventures that have their own employees and operating expenses, and to which the Company generally makes a capital contribution. The Company accounts for these joint ventures either as consolidated entities or equity method investments based on the criteria further discussed below.

The Company follows guidance on the consolidation of variable interest entities (VIEs) that requires companies to utilize a qualitative approach to determine whether it is the primary beneficiary of a VIE. The process for identifying the primary beneficiary of a VIE requires consideration of the factors that indicate a party has the power to direct the activities that most significantly impact the joint venture's economic performance, including powers granted to the joint venture's program manager, powers contained in the joint venture governing board and, to a certain extent, a company's economic interest in the joint venture. The Company analyzes its joint ventures and classifies them as either:

•a VIE that must be consolidated because the Company is the primary beneficiary or the joint venture is not a VIE and the Company holds the majority voting interest with no significant participative rights available to the other partners; or

•a VIE that does not require consolidation and is treated as an equity method investment because the Company is not the primary beneficiary or the joint venture is not a VIE and the Company does not hold the majority voting interest.

As part of the above analysis, if it is determined that the Company has the power to direct the activities that most significantly impact the joint venture's economic performance, the Company considers whether or not it has the obligation to absorb losses or rights to receive benefits of the VIE that could potentially be significant to the VIE.

Contractually required support provided to the Company's joint ventures is discussed in Note 18.

Summary of financial information of the consolidated joint ventures is as follows:

	September 30, 2017		September 30, 2016
	(in millions)
Current assets	$	832.1	$	684.1
Non-current assets		188.8		230.8

Total assets	$	1,020.9	$	914.9


Current liabilities	$	524.9	$	407.4
Non-current liabilities		12.4		12.4

Total liabilities		537.3		419.8
Total AECOM equity		274.7		318.0
Noncontrolling interests		208.9		177.1

Total owners' equity		483.6		495.1

Total liabilities and owners' equity	$	1,020.9	$	914.9

Total revenue of the consolidated joint ventures was $1,933.5 million, $1,935.2 million, and $2,368.0 million for the years ended September 30, 2017, 2016 and 2015, respectively. The assets of the Company's consolidated joint ventures are restricted for use only by the particular joint venture and are not available for the general operations of the Company.

Summary of financial information of the unconsolidated joint ventures, as derived from their unaudited financial statements, is as follows:

	September 30, 2017		September 30, 2016
	(in millions)
Current assets	$	1,912.2	$	1,407.0
Non-current assets		749.8		499.4

Total assets	$	2,662.0	$	1,906.4


Current liabilities	$	1,570.2	$	977.3
Non-current liabilities		185.1		146.2

Total liabilities		1,755.3		1,123.5
Joint ventures' equity		906.7		782.9

Total liabilities and joint ventures' equity	$	2,662.0	$	1,906.4


AECOM's investment in joint ventures	$	364.2	$	330.5

	Twelve Months Ended
	September 30, 2017		September 30, 2016
	(in millions)
Revenue	$	5,561.8	$	4,871.8
Cost of revenue		5,305.5		4,618.3

Gross profit	$	256.3	$	253.5

Net income	$	244.8	$	233.9

Summary of AECOM's equity in earnings of unconsolidated joint ventures is as follows:

	Fiscal Year Ended
	September 30, 2017		September 30, 2016		September 30, 2015
	(in millions)
Pass through joint ventures	$	36.6	$	21.9	$	26.2
Other joint ventures		105.0		82.1		80.0

Total	$	141.6	$	104.0	$	106.2

Included in equity of earnings above, the Company recorded a gain of $52 million from a sale of its 50% equity interest in Provost Square I LLC, an unconsolidated joint venture that invested in a real estate development in New Jersey, in fiscal year ended September 30, 2017.

Pension Benefit Obligations

12 Months Ended

Sep. 30, 2017

Pension Benefit Obligations

Pension Benefit Obligations

7. Pension Benefit Obligations

In the U.S., the Company sponsors various qualified defined benefit pension plans. Benefits under these plans generally are based on the employee's years of creditable service and compensation; however, all U.S. defined benefit plans are closed to new participants and have frozen accruals. The Company adopted an amendment to freeze benefits under the URS Federal Services, Inc. Employees Retirement Plan during the three months ended December 31, 2015, which resulted in the curtailment gain listed below.

The Company also sponsors various non-qualified plans in the U.S.; all of these plans are frozen. Outside the U.S., the Company sponsors various pension plans, which are appropriate to the country in which the Company operates, some of which are government mandated.

The following tables provide reconciliations of the changes in the U.S. and international plans' benefit obligations, reconciliations of the changes in the fair value of assets for the last three years ended September 30, and reconciliations of the funded status as of September 30 of each year.

	Fiscal Year Ended
	September 30, 2017						September 30, 2016						September 30, 2015
	U.S.			Int'l			U.S.			Int'l			U.S.			Int'l
	(in millions)
Change in benefit obligation:
Benefit obligation at beginning of year	$	720.0		$	1,406.2		$	718.2		$	1,239.2		$	217.0		$	676.6
Service cost		4.3			1.3			4.3			1.0			6.8			1.1
Participant contributions		0.1			0.4			0.1			0.5			0.4			0.5
Interest cost		19.2			28.3			22.0			39.2			28.2			47.1
Benefits and expenses paid		(37.9	)		(48.3	)		(37.4	)		(41.9	)		(33.9	)		(41.0	)
Actuarial (gain) loss		(22.7	)		(98.6	)		52.3			377.1			(41.0	)		10.6
Plan settlements		—			—			(32.9	)		(0.7	)		(20.1	)		(2.5	)
Plan amendments		—			—			0.2			—			—			—
Plan curtailments		—			—			(6.8	)		—			—			—
Net transfer in/(out)/acquisitions		—			—			—			—			560.8			618.6
Foreign currency translation loss (gain)		—			44.2			—			(208.2	)		—			(71.8	)

Benefit obligation at end of year	$	683.0		$	1,333.5		$	720.0		$	1,406.2		$	718.2		$	1,239.2

	Fiscal Year Ended
	September 30, 2017						September 30, 2016						September 30, 2015
	U.S.			Int'l			U.S.			Int'l			U.S.			Int'l
	(in millions)
Change in plan assets
Fair value of plan assets at beginning of year	$	456.9		$	973.2		$	459.0		$	925.8		$	139.7		$	532.6
Actual return on plan assets		39.0			9.6			49.6			215.9			(2.8	)		49.9
Employer contributions		12.3			25.8			18.5			20.2			42.1			24.4
Participant contributions		0.1			0.4			0.1			0.5			0.4			0.5
Benefits and expenses paid		(37.9	)		(48.3	)		(37.4	)		(41.9	)		(33.9	)		(41.0	)
Plan settlements		—			—			(32.9	)		(0.7	)		(20.1	)		(2.5	)
Net transfer in/(out)/acquisitions		—			—			—			—			333.6			415.5
Foreign currency translation gain (loss)		—			32.4			—			(146.6	)		—			(53.6	)

Fair value of plan assets at end of year	$	470.4		$	993.1		$	456.9		$	973.2		$	459.0		$	925.8

	Fiscal Year Ended
	September 30, 2017						September 30, 2016						September 30, 2015
	U.S.			Int'l			U.S.			Int'l			U.S.			Int'l
	(in millions)
Reconciliation of funded status:
Funded status at end of year	$	(212.6	)	$	(340.4	)	$	(263.1	)	$	(433.0	)	$	(259.2	)	$	(313.4	)
Contribution made after measurement date		N/A			N/A			N/A			N/A			N/A			N/A

Net amount recognized at end of year	$	(212.6	)	$	(340.4	)	$	(263.1	)	$	(433.0	)	$	(259.2	)	$	(313.4	)

The following table sets forth the amounts recognized in the consolidated balance sheets as of September 30, 2017, 2016 and 2015:

	Fiscal Year Ended
	September 30, 2017						September 30, 2016						September 30, 2015
	U.S.			Int'l			U.S.			Int'l			U.S.			Int'l
	(in millions)
Amounts recognized in the consolidated balance sheets:
Other non-current assets	$	2.3		$	13.9		$	2.0		$	5.3		$	1.6		$	1.7
Accrued expenses and other current liabilities		(10.1	)		—			(9.3	)		—			(10.6	)		—
Pension benefit obligations		(204.8	)		(354.3	)		(255.8	)		(438.3	)		(250.2	)		(315.1	)

Net amount recognized in the balance sheet	$	(212.6	)	$	(340.4	)	$	(263.1	)	$	(433.0	)	$	(259.2	)	$	(313.4	)

The following table details the reconciliation of amounts in the consolidated statements of stockholders' equity for the fiscal years ended September 30, 2017, 2016 and 2015:

	Fiscal Year Ended
	September 30, 2017						September 30, 2016						September 30, 2015
	U.S.			Int'l			U.S.			Int'l			U.S.			Int'l
	(in millions)
Reconciliation of amounts in consolidated statements of stockholders' equity:
Prior service (cost) credit	$	(0.2	)	$	4.4		$	(0.2	)	$	4.4		$	—		$	5.3
Net loss		(94.6	)		(263.7	)		(129.6	)		(343.3	)		(99.3	)		(183.6	)

Total recognized in accumulated other comprehensive loss	$	(94.8	)	$	(259.3	)	$	(129.8	)	$	(338.9	)	$	(99.3	)	$	(178.3	)

The following table details the components of net periodic benefit cost for the Company's pension plans for fiscal years ended September 30, 2017, 2016 and 2015:

	Fiscal Year Ended
	September 30, 2017						September 30, 2016						September 30, 2015
	U.S.			Int'l			U.S.			Int'l			U.S.			Int'l
	(in millions)
Components of net periodic (benefit) cost:
Service costs	$	4.3		$	1.3		$	4.3		$	1.0		$	6.8		$	1.1
Interest cost on projected benefit obligation		19.2			28.3			22.0			39.2			28.2			47.1
Expected return on plan assets		(31.0	)		(41.5	)		(30.8	)		(48.0	)		(29.4	)		(49.4	)
Amortization of prior service credits		—			(0.2	)		—			(0.2	)		—			(0.2	)
Amortization of net loss		4.3			13.0			4.0			5.4			4.3			5.9
Curtailment gain recognized		—			—			(6.8	)		—			—			—
Settlement (gain) loss recognized		—			—			(0.9	)		0.1			0.6			0.7

Net periodic (benefit) cost	$	(3.2	)	$	0.9		$	(8.2	)	$	(2.5	)	$	10.5		$	5.2

The amount, net of applicable deferred income taxes, included in other comprehensive income arising from a change in net prior service cost and net gain/loss was $27.6 million, $26.2 million, and $6.9 million in the years ended September 30, 2017, 2016 and 2015, respectively.

Amounts included in accumulated other comprehensive loss as of September 30, 2017 that are expected to be recognized as components of net periodic benefit cost during fiscal 2018 are (in millions):

	U.S.			Int'l
Amortization of prior service credit	$	—		$	0.2
Amortization of net actuarial losses		(4.0	)		(8.2	)

Total	$	(4.0	)	$	(8.0	)

The table below provides additional year-end information for pension plans with accumulated benefit obligations in excess of plan assets.

	Fiscal Year Ended
	September 30, 2017				September 30, 2016				September 30, 2015
	U.S.		Int'l		U.S.		Int'l		U.S.		Int'l
	(in millions)
Projected benefit obligation	$	658.4	$	1,158.3	$	694.8	$	1,220.3	$	692.5	$	1,226.2
Accumulated benefit obligation		658.4		1,145.7		694.8		1,215.7		686.5		1,222.0
Fair value of plan assets		466.4		804.2		453.2		782.1		455.6		911.2

Funding requirements for each pension plan are determined based on the local laws of the country where such pension plan resides. In certain countries, the funding requirements are mandatory while in other countries, they are discretionary. The Company currently intends to contribute $26.8 million to the international plans in fiscal 2018. The required minimum contributions for U.S. plans are not significant. In addition, the Company may make discretionary contributions. The Company currently intends to contribute $12.7 million to U.S. plans in fiscal 2018.

The table below provides the expected future benefit payments, in millions:

Year Ending September 30,	U.S.		Int'l
2018	$	43.0	$	47.4
2019		40.4		47.8
2020		41.5		47.2
2021		41.6		50.3
2022		41.8		52.1
2023 - 2027		205.0		291.9

Total	$	413.3	$	536.7

The underlying assumptions for the pension plans are as follows:

	Fiscal Year Ended
	September 30, 2017						September 30, 2016						September 30, 2015
	U.S.			Int'l			U.S.			Int'l			U.S.			Int'l
Weighted-average assumptions to determine benefit obligation:
Discount rate		3.64	%		2.67	%		3.41	%		2.35	%		4.10	%		3.80	%
Salary increase rate		N/A			2.76	%		N/A			2.61	%		3.81	%		2.51	%
Weighted-average assumptions to determine net periodic benefit cost:
Discount rate		3.41	%		2.35	%		4.10	%		3.80	%		3.88	%		3.92	%
Salary increase rate		N/A			2.61	%		N/A			2.65	%		4.50	%		2.65	%
Expected long-term rate of return on plan assets		7.00	%		5.10	%		6.72	%		5.74	%		6.73	%		6.00	%

Pension costs are determined using the assumptions as of the beginning of the plan year. The funded status is determined using the assumptions as of the end of the plan year.

The following table summarizes the Company's target allocation for 2017 and pension plan asset allocation, both U.S. and international, as of September 30, 2017 and 2016:

							Percentage of Plan Assets as of September 30,
	Target Allocations						2017						2016
	U.S.			Int'l			U.S.			Int'l			U.S.			Int'l
Asset Category:
Equities		43	%		28	%		43	%		27	%		42	%		28	%
Debt		48			35			47			38			49			34
Cash		1			5			1			2			1			7
Property and other		8			32			9			33			8			31

Total		100	%		100	%		100	%		100	%		100	%		100	%

The Company's domestic and foreign plans seek a competitive rate of return relative to an appropriate level of risk depending on the funded status and obligations of each plan and typically employ both active and passive investment management strategies. The Company's risk management practices include diversification across asset classes and investment styles and periodic rebalancing toward asset allocation targets. The target asset allocation selected for each plan reflects a risk/return profile that the Company believes is appropriate relative to each plan's liability structure and return goals.

To develop the expected long-term rate of return on assets assumption, the Company considered the historical returns and the future expectations for returns for each asset class, as well as the target asset allocation of the pension portfolio and the diversification of the portfolio. This resulted in the selection of a 7.00% and 5.10% weighted-average long-term rate of return on assets assumption for the fiscal year ended September 30, 2017 for U.S. and non-U.S. plans, respectively.

As of September 30, 2017, the fair values of the Company's pension plan assets by major asset categories were as follows:

			Fair Value Measurement as of September 30, 2017
	Total Carrying Value as of September 30, 2017		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in millions)
Cash and cash equivalents	$	22.9	$	13.1	$	9.8	$	—
Equity securities
Global equity securities		0.8		—		0.8		—
Domestic equity securities		7.1		6.2		0.9		—
Investment funds
Diversified funds		212.8		—		212.8		—
Equity funds		467.9		6.4		461.5		—
Fixed income funds		610.6		3.5		607.1		—
Hedge funds		110.1		—		69.9		40.2
Assets held by insurance company		31.3		—		31.3		—

Total	$	1,463.5	$	29.2	$	1,394.1	$	40.2

As of September 30, 2016, the fair values of the Company's post-retirement benefit plan assets by major asset categories are as follows:

			Fair Value Measurement as of September 30, 2016
	Total Carrying Value as of September 30, 2016		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in millions)
Cash and cash equivalents	$	70.6	$	14.3	$	56.3	$	—
Equity securities
Global equity securities		49.4		—		49.4		—
Domestic equity securities		57.1		—		57.1		—
Investment funds
Diversified funds		223.1		—		223.1		—
Equity funds		362.0		5.1		356.9		—
Fixed income funds		548.5		3.7		544.8		—
Hedge funds		62.5		—		48.4		14.1
Assets held by insurance company		32.3		—		32.3		—
Other		24.6		—		24.6		—

Total	$	1,430.1	$	23.1	$	1,392.9	$	14.1

Changes for the year ended September 30, 2017, in the fair value of the Company's recurring post-retirement plan Level 3 assets are as follows:

	September 30, 2016 Beginning balance		Actual return on plan assets, relating to assets still held at reporting date			Actual return on plan assets, relating to assets sold during the period		Purchases, sales and settlements		Transfer into / (out of) Level 3		Change due to exchange rate changes		September 30, 2017 Ending balance
	(in millions)
Investment funds
Hedge funds	$	14.1	$	(0.2	)	$	—	$	—	$	26.3	$	—	$	40.2

Changes for the year ended September 30, 2016, in the fair value of the Company's recurring post-retirement plan Level 3 assets are as follows:

	September 30, 2015 Beginning balance		Actual return on plan assets, relating to assets still held at reporting date		Actual return on plan assets, relating to assets sold during the period		Purchases, sales and settlements		Transfer into / (out of) Level 3		Change due to exchange rate changes		September 30, 2016 Ending balance
	(in millions)
Investment funds
Hedge funds	$	13.6	$	0.5	$	—	$	—	$	—	$	—	$	14.1

Cash equivalents are mostly comprised of short-term money-market instruments and are valued at cost, which approximates fair value.

For equity investment funds not traded on an active exchange, or if the closing price is not available, the trustee obtains indicative quotes from a pricing vendor, broker, or investment manager. These funds are categorized as Level 2 if the custodian obtains corroborated quotes from a pricing vendor or categorized as Level 3 if the custodian obtains uncorroborated quotes from a broker or investment manager.

Fixed income investment funds categorized as Level 2 are valued by the trustee using pricing models that use verifiable observable market data (e.g., interest rates and yield curves observable at commonly quoted intervals), bids provided by brokers or dealers, or quoted prices of securities with similar characteristics.

Hedge funds categorized as Level 3 are valued based on valuation models that include significant unobservable inputs and cannot be corroborated using verifiable observable market data. Hedge funds are valued by independent administrators. Depending on the nature of the assets, the general partners or independent administrators use both the income and market approaches in their models. The market approach consists of analyzing market transactions for comparable assets while the income approach uses earnings or the net present value of estimated future cash flows adjusted for liquidity and other risk factors. As of September 30, 2017, there were no material changes to the valuation techniques.

Multiemployer Pension Plans

The Company participates in over 200 construction-industry multiemployer pension plans. Generally, the plans provide defined benefits to substantially all employees covered by collective bargaining agreements. Under the Employee Retirement Income Security Act, a contributor to a multiemployer plan is liable, upon termination or withdrawal from a plan, for its proportionate share of a plan's unfunded vested liability. The Company's aggregate contributions to these multiemployer plans were $48.8 million and $49.5 million for the years ended September 30, 2017 and 2016, respectively. At September 30, 2017 and 2016, none of the plans in which the Company participates are individually significant to its consolidated financial statements.

Debt

12 Months Ended

Sep. 30, 2017

Debt

Debt

8. Debt

Debt consisted of the following:

	September 30, 2017			September 30, 2016
	(in millions)
2014 Credit Agreement	$	908.7		$	1,954.9
2014 Senior Notes		1,600.0			1,600.0
2017 Senior Notes		1,000.0			—
URS Senior Notes		247.7			427.7
Other debt		140.0			142.7

Total debt		3,896.4			4,125.3
Less: Current portion of debt and short-term borrowings		(142.0	)		(366.3	)
Less: Unamortized debt issuance costs		(52.3	)		(56.8	)

Long-term debt	$	3,702.1		$	3,702.2

The following table presents, in millions, scheduled maturities of the Company's debt as of September 30, 2017:

Fiscal Year
2018	$	142.0
2019		154.4
2020		122.6
2021		603.7
2022		256.7
Thereafter		2,617.0

Total	$	3,896.4

2014 Credit Agreement

The Company entered into a credit agreement (Credit Agreement) on October 17, 2014, as amended, consisting of (i) a term loan A facility in an aggregate principal amount of $1.925 billion, (ii) a term loan B facility in an aggregate principal amount of $0.76 billion and (iii) a revolving credit facility in an aggregate principal amount of $1.05 billion. These facilities under the Credit Agreement may be increased by an additional amount of up to $500 million. The Credit Agreement's term extends to September 29, 2021 with respect to the revolving credit facility and the term loan A facility and October 17, 2021 with respect to the term loan B facility, although the term loan B facility was paid in full on February 21, 2017. Some subsidiaries of the Company (Guarantors) have guaranteed the obligations of the borrowers under the Credit Agreement. The borrowers' obligations under the Credit Agreement are secured by a lien on substantially all of the assets of the Company and the Guarantors pursuant to a security and pledge agreement (Security Agreement). The collateral under the Security Agreement is subject to release upon fulfillment of certain conditions specified in the Credit Agreement and Security Agreement.

The Credit Agreement contains covenants that limit the ability of the Company and certain of its subsidiaries to, among other things: (i) create, incur, assume, or suffer to exist liens; (ii) incur or guarantee indebtedness; (iii) pay dividends or repurchase stock; (iv) enter into transactions with affiliates; (v) consummate asset sales, acquisitions or mergers; (vi) enter into certain types of burdensome agreements; or (vii) make investments.

On July 1, 2015, the Credit Agreement was amended to revise the definition of "Consolidated EBITDA" to increase the allowance for acquisition and integration expenses related to the acquisition of URS.

On December 22, 2015, the Credit Agreement was amended to further revise the definition of "Consolidated EBITDA" by further increasing the allowance for acquisition and integration expenses related to the acquisition of URS and to allow for an internal corporate restructuring primarily involving its international subsidiaries.

On September 29, 2016, the Credit Agreement and the Security Agreement were amended to (1) lower the applicable interest rate margins for the term loan A and the revolving credit facilities, and lower the applicable letter of credit fees and commitment fees to the revised consolidated leverage levels; (2) extend the term of the term loan A and the revolving credit facility to September 29, 2021; (3) add a new delayed draw term loan A facility tranche in the amount of $185.0 million; (4) replace the then existing $500 million performance letter of credit facility with a $500 million basket to enter into secured letters of credit outside the Credit Agreement; and (5) revise certain covenants, including the Maximum Consolidated Leverage Ratio so that the step down from a 5.00 to a 4.75 leverage ratio is effective as of March 31, 2017 as well as the investment basket for its AECOM Capital business.

On March 31, 2017, the Credit Agreement was amended to (1) expand the ability of restricted subsidiaries to borrow under "Incremental Term Loans"; (2) revise the definition of "Working Capital" as used in "Excess Cash Flow"; (3) revise the definitions for "Consolidated EBITDA" and "Consolidated Funded Indebtedness" to reflect the expected gain and debt repayment of an AECOM Capital disposition, which disposition was completed on April 28, 2017; and (4) amend provisions relating to the Company's ability to undertake certain internal restructuring steps to accommodate changes in tax laws.

Under the Credit Agreement, the Company is subject to a maximum consolidated leverage ratio and minimum consolidated interest coverage ratio at the end of each fiscal quarter. The Company's Consolidated Leverage Ratio was 4.0 at September 30, 2017. The Company's Consolidated Interest Coverage Ratio was 4.7 at September 30, 2017. As of September 30, 2017, the Company was in compliance with the covenants of the Credit Agreement.

At September 30, 2017 and 2016, outstanding standby letters of credit totaled $58.1 million and $92.3 million, respectively, under the Company's revolving credit facilities. As of September 30, 2017 and 2016, the Company had $991.9 million and $888.4 million, respectively, available under its revolving credit facility.

2014 Senior Notes

On October 6, 2014, the Company completed a private placement offering of $800,000,000 aggregate principal amount of its unsecured 5.750% Senior Notes due 2022 (2022 Notes) and $800,000,000 aggregate principal amount of its unsecured 5.875% Senior Notes due 2024 (the 2024 Notes and, together with the 2022 Notes, the 2014 Senior Notes).

As of September 30, 2017, the estimated fair value of its 2014 Senior Notes was approximately $836.0 million for the 2022 Notes and $884.0 million for the 2024 Notes. The fair value of the 2014 Senior Notes as of September 30, 2017 was derived by taking the mid-point of the trading prices from an observable market input (Level 2) in the secondary bond market and multiplying it by the outstanding balance of the 2014 Senior Notes.

At any time prior to October 15, 2017, the Company may redeem all or part of the 2022 Notes, at a redemption price equal to 100% of their principal amount, plus a "make whole" premium as of the redemption date, and accrued and unpaid interest (subject to the rights of holders of record on the relevant record date to receive interest due on the relevant interest payment date). In addition, at any time prior to October 15, 2017, the Company may redeem up to 35% of the original aggregate principal amount of the 2022 Notes with the proceeds of one or more equity offerings, at a redemption price equal to 105.750%, plus accrued and unpaid interest. Furthermore, at any time on or after October 15, 2017, the Company may redeem the 2022 Notes, in whole or in part, at once or over time, at the specified redemption prices plus accrued and unpaid interest thereon to the redemption date. At any time prior to July 15, 2024, the Company may redeem on one or more occasions all or part of the 2024 Notes at a redemption price equal to the sum of (i) 100% of the principal amount thereof, plus (ii) a "make-whole" premium as of the date of the redemption, plus any accrued and unpaid interest to the date of redemption. In addition, on or after July 15, 2024, the 2024 Notes may be redeemed at a redemption price of 100% of the principal amount thereof, plus accrued and unpaid interest to the date of redemption.

The indenture pursuant to which the 2014 Senior Notes were issued contains customary events of default, including, among other things, payment default, exchange default, failure to provide certain notices thereunder and certain provisions related to bankruptcy events. The indenture also contains customary negative covenants.

On November 2, 2015, the Company completed an exchange offer to exchange the unregistered 2014 Senior Notes for registered notes, as well as all related guarantees.

The Company was in compliance with the covenants relating to the 2014 Senior Notes as of September 30, 2017.

2017 Senior Notes

On February 21, 2017, the Company completed a private placement offering of $1,000,000,000 aggregate principal amount of its unsecured 5.125% Senior Notes due 2027 (the 2017 Senior Notes) and used the note proceeds to immediately retire the remaining $127.6 million outstanding on the term loan B facility as well as repay $600 million of the term loan A facility and $250 million of the revolving credit facility under its Credit Agreement.

As of September 30, 2017, the estimated fair value of the Company's 2017 Senior Notes was approximately $1,031.3 million. The fair value of the Company's 2017 Senior Notes as of September 30, 2017 was derived by taking the mid-point of the trading prices from an observable market input (Level 2) in the secondary bond market and multiplying it by the outstanding balance of the 2017 Senior Notes. Interest will be payable on the 2017 Senior Notes at a rate of 5.125% per annum. Interest on the 2017 Senior Notes will be payable semi-annually on March 15 and September 15 of each year, commencing on September 15, 2017. The 2017 Senior Notes will mature on March 15, 2027.

At any time and from time to time prior to December 15, 2026, the Company may redeem all or part of the 2017 Senior Notes, at a redemption price equal to 100% of their principal amount, plus a "make whole" premium as of the redemption date, and accrued and unpaid interest to the redemption date.

In addition, at any time and from time to time prior to March 15, 2020, the Company may redeem up to 35% of the original aggregate principal amount of the 2017 Senior Notes with the proceeds of one or more qualified equity offerings, at a redemption price equal to 105.125%, plus accrued and unpaid interest. Furthermore, at any time on or after December 15, 2026, the Company may redeem on one or more occasions all or part of the 2017 Senior Notes at a redemption price equal to 100% of their principal amount, plus accrued and unpaid interest.

The indenture pursuant to which the 2017 Senior Notes were issued contains customary events of default, including, among other things, payment default, exchange default, failure to provide certain notices thereunder and certain provisions related to bankruptcy events. The indenture also contains customary negative covenants.

The Company and the Guarantors filed a registration statement on Form S-4 with the SEC on May 11, 2017 that was declared effective by the SEC on May 25, 2017 to exchange the unregistered 2017 Senior Notes for registered notes and guarantees having terms substantially identical in all material respects. On June 30, 2017, the Company completed its exchange offer by exchanging $999,074,000 aggregate principal amount of the unregistered 2017 Senior Notes with registered notes, as well as all related guarantees. $926,000 aggregate principal amount of the unregistered 2017 Senior Notes remained outstanding as of September 30, 2017.

The Company was in compliance with the covenants relating to its 2017 Senior Notes as of September 30, 2017.

URS Senior Notes

In connection with the URS acquisition, the Company assumed the URS 3.85% Senior Notes due 2017 (2017 URS Senior Notes) and the URS 5.00% Senior Notes due 2022 (2022 URS Senior Notes), totaling $1.0 billion (URS Senior Notes). The URS acquisition triggered change in control provisions in the URS Senior Notes that allowed the holders of the URS Senior Notes to redeem their URS Senior Notes at a cash price equal to 101% of the principal amount and, accordingly, the Company redeemed $572.3 million of the URS Senior Notes on October 24, 2014. The remaining 2017 URS Senior Notes matured and were fully redeemed on April 3, 2017 for $179.2 million using proceeds from a $185 million delayed draw term loan A facility tranche under the Credit Agreement. The 2022 URS Senior Notes are general unsecured senior obligations of AECOM Global II, LLC (as successor in interest to URS) and are fully and unconditionally guaranteed on a joint-and-several basis by certain former URS domestic subsidiary guarantors.

As of September 30, 2017, the estimated fair value of the 2022 URS Senior Notes was approximately $259.7 million. The carrying value of the 2022 URS Senior Notes on the Company's Consolidated Balance Sheets as of September 30, 2017 was $247.7 million. The fair value of the 2022 URS Senior Notes as of September 30, 2017 was derived by taking the mid-point of the trading prices from an observable market input (Level 2) in the secondary bond market and multiplying it by the outstanding balance of the 2022 URS Senior Notes.

As of September 30, 2017, the Company was in compliance with the covenants relating to the 2022 URS Senior Notes.

Other Debt

Other debt consists primarily of obligations under capital leases and loans, and unsecured credit facilities. The Company's unsecured credit facilities are primarily used for standby letters of credit issued for payment of performance guarantees. At September 30, 2017 and 2016, these outstanding standby letters of credit totaled $445.7 million and $382.2 million, respectively. As of September 30, 2017, the Company had $502.3 million available under these unsecured credit facilities.

Effective Interest Rate

The Company's average effective interest rate on its total debt, including the effects of the interest rate swap agreements, during the years ended September 30, 2017, 2016 and 2015 was 4.6%, 4.4% and 4.2%, respectively.

Interest expense in the consolidated statements of operations for the years ended September 30, 2017 and 2016 included amortization of deferred debt issuance costs of $17.5 million and $30.9 million, respectively.

Derivative Financial Instruments and Fair Value Measurements

12 Months Ended

Sep. 30, 2017

Derivative Financial Instruments and Fair Value Measurements

Derivative Financial Instruments and Fair Value Measurements

9. Derivative Financial Instruments and Fair Value Measurements

The Company uses certain interest rate derivative contracts to hedge interest rate exposures on the Company's variable rate debt. The Company enters into foreign currency derivative contracts with financial institutions to reduce the risk that its cash flows and earnings will be adversely affected by foreign currency exchange rate fluctuations. The Company's hedging program is not designated for trading or speculative purposes.

The Company recognizes derivative instruments as either assets or liabilities on the accompanying consolidated balance sheets at fair value. The Company records changes in the fair value (i.e., gains or losses) of the derivatives that have been designated as accounting hedges in the accompanying consolidated statements of operations as cost of revenue, interest expense or to accumulated other comprehensive loss in the accompanying consolidated balance sheets.

Cash Flow Hedges

The Company uses interest rate swap agreements designated as cash flow hedges to fix the variable interest rates on portions of the Company's debt. The Company also uses foreign currency contracts designated as cash flow hedges to hedge forecasted revenue transactions denominated in currencies other than the U.S. dollar. The Company initially reports any gain on the effective portion of a cash flow hedge as a component of accumulated other comprehensive loss. Depending on the type of cash flow hedge, the gain is subsequently reclassified to either interest expense when the interest expense on the variable rate debt is recognized, or to cost of revenue when the hedged revenues are recorded. If the hedged transaction becomes probable of not occurring, any gain or loss related to interest rate swap agreements or foreign currency contracts would be recognized in other income (expense). Further, the Company excludes the change in the time value of the foreign currency contracts from the assessment of hedge effectiveness. The Company records the premium paid or time value of a contract on the date of purchase as an asset. Thereafter, the Company recognizes any change to this time value in cost of revenue.

The notional principal, fixed rates and related expiration dates of the Company's outstanding interest rate swap agreements were as follows:

September 30, 2017
Notional Amount (in millions)		Fixed Rate			Expiration Date
$	300.0		1.63	%	June 2018
	300.0		1.54	%	September 2018

September 30, 2016
Notional Amount (in millions)		Fixed Rate			Expiration Date
$	300.0		1.63	%	June 2018
	300.0		1.54	%	September 2018

The notional principal of outstanding foreign currency contracts to purchase Australian dollars (AUD) was AUD 15.1 million (or $11.3 million) at September 30, 2017. The notional principal of outstanding foreign currency contracts to purchase Australian dollars with U.S. dollars was AUD 58.6 million (or $43.4 million) at September 30, 2016.

Other Foreign Currency Forward Contracts

The Company uses foreign currency forward contracts which are not designated as accounting hedges to hedge intercompany transactions and other monetary assets or liabilities denominated in currencies other than the functional currency of a subsidiary. Gains and losses on these contracts were not material for the years ended September 30, 2017, 2016 and 2015.

Fair Value Measurements

The Company's non-pension financial assets and liabilities recorded at fair values relate to derivative instruments and were not material at September 30, 2017 or 2016.

See Note 17 for accumulated balances and reporting period activities of derivatives related to reclassifications out of accumulated other comprehensive income or loss for the years ended September 30, 2017, 2016 and 2015. Amounts recognized in accumulated other comprehensive loss from the Company's foreign currency options were immaterial for all years presented. Amounts reclassified from accumulated other comprehensive loss into income from the foreign currency options were immaterial for all years presented. Additionally, there were no losses recognized in income due to amounts excluded from effectiveness testing from the Company's interest rate swap agreements.

During the year ended September 30, 2015, the Company entered into a contingent consideration arrangement in connection with a business acquisition. Under the arrangement, the Company agreed to pay cash to the sellers if certain financial performance thresholds are achieved in the future. The fair value of the contingent consideration liability, net of amounts paid, as of September 30, 2017 and 2016 was $13 million and $39 million, respectively, which decreased due to payments of approximately $21 million, and a change in estimated fair value during the year ended September 30, 2017. This liability is a Level 3 fair value measurement recorded within other accrued liabilities, and was valued based on estimated future net cash flows. Any future changes in the fair value of this contingent consideration liability will be recognized in earnings during the applicable period.

- Definition

The entire disclosure for derivative instruments and hedging activities including, but not limited to, risk management strategies, non-hedging derivative instruments, assets, liabilities, revenue and expenses, and methodologies and assumptions used in determining the amounts.

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+ Details

Concentration of Credit Risk	12 Months Ended
Concentration of Credit Risk	Sep. 30, 2017
Concentration of Credit Risk
Concentration of Credit Risk	10. Concentration of Credit Risk Financial instruments which potentially subject the Company to concentrations of credit risk consist principally of cash investments and trade receivables. The Company's cash balances and short-term investments are maintained in accounts held by major banks and financial institutions located primarily in the U.S., Canada, Europe, Australia, Middle East and Hong Kong. If the Company extends significant credit to clients in a specific geographic area or industry, the Company may experience disproportionately high levels of default if those clients are adversely affected by factors particular to their geographic area or industry. Concentrations of credit risk with respect to trade receivables are limited due to the large number of customers comprising the Company's customer base, including, in large part, governments, government agencies and quasi-government organizations, and their dispersion across many different industries and geographies. See Note 19 regarding the Company's foreign revenues. In order to mitigate credit risk, the Company continually reviews the credit worthiness of its major private clients.

Leases

12 Months Ended

Sep. 30, 2017

Leases

Leases

11. Leases

The Company and its subsidiaries are lessees in non-cancelable leasing agreements for office buildings and equipment. The related payments are expensed on a straight-line basis over the lease term, including, as applicable, any free-rent period during which the Company has the right to use the asset. For leases with renewal options where the renewal is reasonably assured, the lease term, including the renewal period is used to determine the appropriate lease classification and to compute periodic rental expense. The following table presents, in millions, amounts payable under non-cancelable operating lease commitments during the following fiscal years:

Year Ending September 30,
2018	$	259.1
2019		214.8
2020		174.2
2021		139.7
2022		114.9
Thereafter		460.1

Total	$	1,362.8

Rent expense for leases for the years ended September 30, 2017, 2016 and 2015 was approximately $265.9 million, $383.7 million, and $395.9 million, respectively. When the Company is required to restore leased facilities to original condition, provisions are made over the period of the lease.

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Sep. 30, 2017
Stockholders' Equity
Stockholders' Equity	12. Stockholders' Equity Common Stock Units—Common stock units are only redeemable for common stock. In the event of liquidation of the Company, holders of stock units are entitled to no greater rights than holders of common stock. See also Note 13.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

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+ Details

Share-Based Payments

12 Months Ended

Sep. 30, 2017

Share-Based Payments

Share-Based Payments

13. Share-Based Payments

Defined Contribution Plans—Substantially all permanent domestic employees are eligible to participate in defined contribution plans provided by the Company. Under these plans, participants may make contributions into a variety of funds, including a fund that is fully invested in Company stock. Employees are not required to allocate any funds to Company stock; however, the Company does provide an annual Company match in AECOM shares. Employees may generally reallocate their account balances on a daily basis; however, employees classified as insiders are restricted under the Company's insider trading policy. Compensation expense relating to these employer contributions to purchase AECOM stock under defined contribution plans for fiscal years ended September 30, 2017, 2016 and 2015 was $32.9 million, $26.8 million, and $13.3 million, respectively.

Stock Incentive Plans—Under the 2016 Stock Incentive Plan, the Company has up to 13.6 million securities remaining available for future issuance as of September 30, 2017. Stock options may be granted to employees and non-employee directors with an exercise price not less than the fair market value of the stock on the date of grant. Unexercised options expire seven years after date of grant.

During the three years in the period ended September 30, 2017, option activity was as follows:

	Number of Options (in millions)			Weighted Average Exercise Price
Balance, September 30, 2014		1.6			27.69
Granted		—			—
Exercised		(0.3	)		24.98
Cancelled		—			—

Balance, September 30, 2015		1.3			28.26


Granted		—			—
Exercised		(0.4	)		23.96
Cancelled		—			—

Balance, September 30, 2016		0.9			30.36


Granted		—			—
Exercised		(0.2	)		26.42
Cancelled		—			—

Balance, September 30, 2017		0.7			31.11


Exercisable as of September 30, 2015		0.7			25.04


Exercisable as of September 30, 2016		0.3			26.99


Exercisable as of September 30, 2017		0.1			27.79

The following table summarizes information concerning outstanding and exercisable options as of September 30, 2017:

	Options Outstanding								Options Exercisable
	Number Outstanding as of September 30, 2017 (in millions)		Weighted Average Remaining Contractual Life		Weighted Average Exercise Price		Aggregate Intrinsic Value (in millions)		Number Exercisable as of September 30, 2017 (in millions)		Weighted Average Remaining Contractual Life		Weighted Average Exercise Price
Range of Exercise Prices
$27.54 - $28.44		0.1		0.27	$	27.79	$	0.9		0.1		0.27	$	27.79
$31.62		0.6		6.43		31.62		3.3		—		—		—

		0.7		5.61		31.11	$	4.2		0.1		0.27		27.79

The remaining contractual life of options outstanding at September 30, 2017 range from 0.19 to 6.43 years and have a weighted average remaining contractual life of 5.61 years. The aggregate intrinsic value of stock options exercised during the years ended September 30, 2017, 2016 and 2015 was $1.2 million, $0.6 million, and $2.1 million, respectively.

The fair value of the Company's employee stock option awards is estimated on the date of grant. The expected term of awards granted represents the period of time the awards are expected to be outstanding. The risk-free interest rate is based on U.S. Treasury bond rates with maturities equal to the expected term of the option on the grant date. The Company uses historical data as a basis to estimate the probability of forfeitures. No stock options were granted during the years ended September 30, 2017 and 2016.

The Company grants stock units to employees under its Performance Earnings Program (PEP), whereby units are earned and issued dependent upon meeting established cumulative performance objectives and vest over a three-year service period. Additionally, the Company issues restricted stock units to employees which are earned based on service conditions. The grant date fair value of PEP awards and restricted stock unit awards is that day's closing market price of the Company's common stock. The weighted average grant date fair value of PEP awards was $38.15, $29.91, and $32.32 during the years ended September 30, 2017, 2016 and 2015, respectively. The weighted average grant date fair value of restricted stock unit awards was $37.96, $29.82, and $31.05 during the years ended September 30, 2017, 2016 and 2015, respectively. Included in the restricted stock unit grants during the twelve months ended September 30, 2015 were 2.6 million restricted stock units with a grant date fair value of $30.04 per share that were converted from unvested URS service based restricted stock awards assumed by the Company in connection with the acquisition of URS. Total compensation expense related to these share-based payments including stock options was $83.8 million, $73.4 million, and $112.2 million during the years ended September 30, 2017, 2016 and 2015, respectively. Included in total compensation expense during the twelve months ended September 30, 2015 was $43.9 million related to the settlement of accelerated URS equity awards with $17.6 million of Company stock and $26.3 million in cash which was classified as acquisition and integration expense. Unrecognized compensation expense related to total share-based payments outstanding as of September 30, 2017 and 2016 was $96.8 million and $91.8 million, respectively, to be recognized on a straight-line basis over the awards' respective vesting periods which are generally three years.

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References + Details

Income Taxes

12 Months Ended

Sep. 30, 2017

Income Taxes

Income Taxes

14. Income Taxes

Income before income taxes included income (loss) from domestic operations of $322.2 million, $51.6 million, and $(214.6) million for fiscal years ended September 30, 2017, 2016 and 2015 and income from foreign operations of $107.0 million, $74.0 million, and $63.1 million for fiscal years ended September 30, 2017, 2016 and 2015.

Income tax (benefit) expense was comprised of:

	Fiscal Year Ended
	September 30, 2017			September 30, 2016			September 30, 2015
	(in millions)
Current:
Federal	$	10.3		$	33.7		$	(67.1	)
State		17.9			12.4			2.6
Foreign		29.3			26.1			37.2

Total current income tax expense (benefit)		57.5			72.2			(27.3	)

Deferred:
Federal		(8.3	)		(63.4	)		(44.2	)
State		10.4			(5.4	)		1.2
Foreign		(51.9	)		(41.3	)		(10.0	)

Total deferred income tax (benefit) expense		(49.8	)		(110.1	)		(53.0	)

Total income tax expense (benefit)	$	7.7		$	(37.9	)	$	(80.3	)

The major elements contributing to the difference between the U.S. federal statutory rate of 35.0% and the effective tax rate are as follows:

	Fiscal Year Ended
	September 30, 2017						September 30, 2016						September 30, 2015
	Amount			%			Amount			%			Amount			%
	(in millions)
Tax at federal statutory rate	$	150.3			35.0	%	$	43.9			35.0	%	$	(53.0	)		35.0	%
State income tax, net of federal benefit		24.3			5.7			5.6			4.5			(2.3	)		1.5
Income tax credits and incentives		(56.8	)		(13.2	)		(24.6	)		(19.6	)		(21.2	)		14.0
Valuation allowance		(51.2	)		(11.9	)		(54.8	)		(43.6	)		30.0			(19.8	)
Exclusion of tax on non-controlling interests		(28.2	)		(6.6	)		(24.7	)		(19.7	)		(29.3	)		19.3
Foreign tax rate differential		(19.2	)		(4.5	)		(19.7	)		(15.7	)		(24.8	)		16.4
Tax exempt income		(17.9	)		(4.2	)		(17.6	)		(14.0	)		(13.2	)		8.7
Foreign residual income		(9.2	)		(2.1	)		17.8			14.2			20.1			(13.3	)
Change in uncertain tax positions		9.5			2.2			(5.0	)		(4.0	)		6.6			(4.3	)
Nondeductible costs		5.8			1.4			6.1			4.8			2.8			(1.8	)
Other items, net		0.3			—			0.5			0.3			1.2			(0.9	)
Change in tax rates		—			—			34.6			27.6			—			—
Nondeductible transaction costs		—			—			—			—			2.8			(1.8	)

Total income tax expense	$	7.7			1.8	%	$	(37.9	)		(30.2	)%	$	(80.3	)		53.0	%

During the years ended September 30, 2016 and 2015, the Company recognized a $10.1 million and $19.4 million tax benefit related to U.S. tax incentives and credits that previously expired on December 31, 2014 and 2013, respectively, and were subsequently extended due to a change in tax law.

The deferred tax assets (liabilities) are as follows:

	Fiscal Year Ended
	September 30, 2017			September 30, 2016
	(in millions)
Deferred tax assets:
Compensation and benefit accruals not currently deductible	$	144.2		$	150.5
Net operating loss carryforwards		338.2			378.0
Self insurance reserves		23.8			24.7
Research and experimentation and other tax credits		167.5			125.3
Pension liability		142.1			180.9
Accrued liabilities		160.7			221.0
Other		25.0			4.3

Total deferred tax assets		1,001.5			1,084.7

Deferred tax liabilities:
Unearned revenue		(190.8	)		(212.6	)
Depreciation and amortization		(158.6	)		(113.0	)
Acquired intangible assets		(121.7	)		(155.5	)
Investment in subsidiaries		(241.2	)		(261.4	)

Total deferred tax liabilities		(712.3	)		(742.5	)

Valuation allowance		(138.4	)		(183.8	)

Net deferred tax assets	$	150.8		$	158.4

As a result of certain realization requirements of ASC 718, the table of deferred tax assets and liabilities does not include certain deferred tax assets as of September 30, 2016, that arose directly from tax deductions related to equity compensation that are greater than the compensation recognized for financial reporting. During the first quarter of 2017, the Company adopted a new accounting standard that amended certain aspects of the accounting for employee share-based payments and as a result recorded an adjustment of $3.8 million to equity to recognize net operating loss carryforwards attributable to excess tax benefits on stock compensation that had not been previously recognized to additional paid in capital.

As of September 30, 2017, the Company has available unused federal, state and foreign net operating loss (NOL) carryforwards of $368.8 million, $899.6 million and $843.8 million, respectively, which expire at various dates over the next several years; some foreign NOL carryforwards never expire. In addition, as of September 30, 2017, the Company has unused federal and state research and development credits of $83.5 million and $21.8 million, respectively, foreign tax credits of $74.8 million, and California Enterprise Zone Tax Credits of $6.6 million which expire at various dates over the next several years.

As of September 30, 2017 and 2016, gross deferred tax assets were $1,001.5 million and $1,084.7 million, respectively. The Company has recorded a valuation allowance of $138.4 million and $183.8 million at September 30, 2017 and 2016, respectively, primarily related to state and foreign net operating loss carryforwards and credits and deferred tax assets related to certain pension obligations (primarily in the United Kingdom and Canada). The Company has performed an assessment of positive and negative evidence, including the nature, frequency, and severity of cumulative financial reporting losses in recent years, the future reversal of existing temporary differences, predictability of future taxable income exclusive of reversing temporary differences of the character necessary to realize the asset, relevant carryforward periods, taxable income in carry-back years if carry-back is permitted under tax law, and prudent and feasible tax planning strategies that would be implemented, if necessary, to protect against the loss of the deferred tax asset that would otherwise expire. Although realization is not assured, based on the Company's assessment, the Company has concluded that it is more likely than not that the remaining gross deferred tax asset (exclusive of deferred tax liabilities) of $863.1 million will be realized and, as such, no additional valuation allowance has been provided. The net decrease in the valuation allowance of $45.3 million is primarily attributable to the release of $59.9 million of valuation allowances for the United Kingdom and the utilization of $4.1 million of foreign net operating loss carryforwards in the current year, partially offset by increases in valuation allowances for unbenefitable losses.

Upon the acquisition of URS in October 2014, the Company had previously recorded a valuation allowance primarily against foreign net operating losses and deferred tax assets related to the pension obligation, consistent with those described above. Tax jurisdictions largely contributing to the URS related valuation allowance included $92.8 million recorded for the United Kingdom, $22.5 million recorded for Canada, $9.3 million recorded for the United States and $2.9 million recorded for Australia. In its determination of the realizability of its deferred tax assets, the Company evaluated positive evidence consisting of positive earnings trends over a sustainable period, positive economic conditions in the industries we operate in, possible prudent and feasible tax planning strategies (net of costs to implement the tax planning strategies) and actual usage of net operating loss and tax credit carryforwards. The Company also evaluated negative evidence consisting of significant net operating loss carryforwards, the cumulative history of losses in recent years, restriction on usage of losses under relevant tax laws, projections of future operations and economic downturns in the industries that we operate in. This evaluation was conducted on a tax jurisdictional basis or legal entity basis, as applicable, and based on the weighing of all positive and negative evidence, a determination was made as to the realizability of the deferred tax assets on that same basis.

Generally, the Company would reverse its valuation allowance in a particular tax jurisdiction if the positive evidence examined, such as projected and sustainable earnings or a tax-planning strategy that allows for the usage of the deferred tax asset, is sufficient to overcome significant negative evidence, such as large net operating loss carryforwards or a cumulative history of losses in recent years.

Valuation allowances in the amount of $59.9 million in the United Kingdom were released due to sufficient positive evidence obtained during the second quarter of 2017. The Company evaluated the new positive evidence against any negative evidence and determined that it is more likely than not that the deferred tax assets will be realized. This positive evidence includes an improvement in earnings, the use of net operating losses on a taxable basis, and better management of pension liabilities due to positive effects of pension asset management and stabilization of interest rates.

Valuation allowances in the amount of $23.3 million in the United Kingdom were released due to sufficient positive evidence obtained during the third quarter of 2016. The Company evaluated the new positive evidence against any negative evidence and determined the valuation allowance was no longer necessary. This new positive evidence included reaching a position of cumulative income over a three-year period and the use of net operating losses on a taxable basis. In addition, the Company's United Kingdom affiliate has strong projected earnings in the United Kingdom.

During the third quarter of 2016, the Company's Australian affiliate made an election in Australia to combine the tax results of the URS Australia business with the AECOM Australia business. This election resulted in the ability to utilize the URS Australia businesses' deferred tax assets against the combined future earnings of the Australian group and accordingly, the valuation allowance of $12.9 million was released.

Certain operations in Canada continue to forecast losses and the valuation allowances could be reduced if the earnings trends reverse. In the United States, the valued deferred tax assets have a restricted life or use under relevant tax law and, therefore, it is unlikely that the valuation allowance related to these assets will reverse. In addition, the Company is continually investigating tax planning strategies that, if prudent and feasible, may be implemented to realize a deferred tax asset that would otherwise expire unutilized. The identification and internal/external approval (as relevant) of such a prudent and feasible tax planning strategy could cause a reduction in the valuation allowance.

In the fourth quarter of 2017, the Company executed international restructuring transactions that resulted in a distribution of current year earnings and profits and the associated foreign tax credits. The distribution resulted in the recognition of a benefit of $25.2 million related to excess foreign tax credits expected to be realized in the foreseeable future. These current year earnings had previously been forecasted to qualify for the indefinite reinvestment criterion. The Company's change in assertion for these investments is a one-time event and does not impact the Company's past or future assertions regarding intent and ability to reinvest indefinitely.

In the third quarter of 2017, the Company recapitalized one of its European subsidiaries which resulted in the Company indefinitely reinvesting a portion of its non-U.S. undistributed earnings that U.S. tax had previously been provided for and released the associated $21.2 million deferred tax liability. These non-U.S. earnings are now intended to be reinvested indefinitely outside of the U.S. to meet the Company's current and future cash needs of its European operations.

Generally, the Company does not provide for U.S. taxes or foreign withholding taxes on gross book-tax differences in its non-U.S. subsidiaries because such basis differences of approximately $1.7 billion are able to and intended to be reinvested indefinitely. If these basis differences were distributed, foreign tax credits could become available under current law to partially or fully reduce the resulting U.S. income tax liability. There may also be additional U.S. or foreign income tax liability upon repatriation, although the calculation of such additional taxes is not practicable. The Company's deferred tax liability related to certain foreign subsidiaries for which the undistributed earnings are not intended to be reinvested indefinitely was $77.0 million and $113.2 million for the years ended September 30, 2017 and 2016, respectively.

As of September 30, 2017 and 2016, the Company had a liability for unrecognized tax benefits, including potential interest and penalties, net of related tax benefit, totaling $109.5 million and $96.8 million, respectively. The gross unrecognized tax benefits as of September 30, 2017 and 2016 were $102.1 million and $87.9 million, respectively, excluding interest, penalties, and related tax benefit. Of the $102.1 million, approximately $86.1 million would be included in the effective tax rate if recognized. A reconciliation of the beginning and ending amount of gross unrecognized tax benefits is as follows:

	Fiscal Year Ended
	September 30, 2017			September 30, 2016
	(in millions)
Balance at the beginning of the year	$	87.9		$	95.2
Gross increase due to acquisitions		—			—
Gross increase in current period's tax positions		10.8			7.6
Gross increase in prior years' tax positions		5.3			5.2
Gross decrease in prior years' tax positions		—			(16.6	)
Decrease due to settlement with tax authorities		(1.0	)		(3.2	)
Decrease due to lapse of statute of limitations		(1.1	)		(1.8	)
Gross change due to foreign exchange fluctuations		0.2			1.5

Balance at the end of the year	$	102.1		$	87.9

The Company classifies interest and penalties related to uncertain tax positions within the income tax expense line in the accompanying consolidated statements of operations. As of September 30, 2017, the accrued interest and penalties were $15.1 million and $4.1 million, respectively, excluding any related income tax benefits. At September 30, 2016, the accrued interest and penalties were $12.5 million and $2.6 million, respectively, excluding any related income tax benefits.

The Company files income tax returns in numerous tax jurisdictions, including the U.S., and numerous U.S. states and non-U.S. jurisdictions around the world. The statute of limitations varies by jurisdiction in which the Company operates. Because of the number of jurisdictions in which the Company files tax returns, in any given year the statute of limitations in certain jurisdictions may expire without examination within the 12-month period from the balance sheet date.

The Company concluded its examination by the U.S. Internal Revenue Service for the fiscal years ended September 30, 2010 and September 30, 2011 in the fourth quarter of 2016, with no material adjustments. The U.S. Internal Revenue Service initiated an examination of URS for the years ended December 31, 2012, December 31, 2013 and October 17, 2014 in August 2016. With a few exceptions, the Company is no longer subject to U.S. state or non-U.S. income tax examinations by tax authorities for years before fiscal 2011.

While it is reasonably possible that the total amounts of unrecognized tax benefits could significantly increase or decrease within the next twelve months, an estimate of the range of possible change cannot be made.

Earnings Per Share

12 Months Ended

Sep. 30, 2017

Earnings Per Share

Earnings Per Share

15. Earnings Per Share

Basic earnings per share (EPS) excludes dilution and is computed by dividing net income attributable to AECOM by the weighted average number of common shares outstanding for the period. Diluted EPS is computed by dividing net income attributable to AECOM by the weighted average number of common shares outstanding and potential common shares for the period. The Company includes as potential common shares the weighted average dilutive effects of equity awards using the treasury stock method. For the periods presented, equity awards excluded from the calculation of potential common shares were not significant. The computation of diluted loss per share for the year ended September 30, 2015 excludes 1.7 million of potential common shares due to their antidilutive effect.

The following table sets forth a reconciliation of the denominators of basic and diluted earnings per share:

	Fiscal Year Ended
	September 30, 2017		September 30, 2016		September 30, 2015
	(in millions)
Denominator for basic earnings per share		155.7		154.8		149.6
Potential common shares		3.4		1.3		—

Denominator for diluted earnings per share		159.1		156.1		149.6

Other Financial Information

12 Months Ended

Sep. 30, 2017

Other Financial Information

Other Financial Information

16. Other Financial Information

Accrued expenses and other current liabilities consist of the following:

	Fiscal Year Ended
	September 30, 2017		September 30, 2016
	(in millions)
Accrued salaries and benefits	$	1,018.5	$	964.9
Accrued contract costs		911.9		1,009.8
Other accrued expenses		315.1		410.1

	$	2,245.5	$	2,384.8

Accrued contract costs above include balances related to professional liability accruals of $547.9 million and $611.0 million as of September 30, 2017 and 2016, respectively. The remaining accrued contract costs primarily relate to costs for services provided by subcontractors and other non-employees. Liabilities recorded related to accrued contract losses were not material as of September 30, 2017 and 2016. The Company did not have material revisions to estimates for contracts where revenue is recognized using the percentage-of-completion method during the twelve months ended September 30, 2017.

During the twelve months ended September 30, 2016, the Company recorded revenue related to the expected accelerated recovery of a pension related entitlement from the federal government of approximately $50 million, which is included in accounts receivable-net at September 30, 2017. The entitlement resulted from pension costs that are reimbursable through certain government contracts in accordance with Cost Accounting Standards. The accelerated recognition resulted from an amendment to freeze pension benefits under URS Federal Services, Inc. Employees Retirement Plan. The actual amount of reimbursement may vary from the Company's expectation.

Reclassifications out of Accumulated Other Comprehensive Loss

12 Months Ended

Sep. 30, 2017

Reclassifications out of Accumulated Other Comprehensive Loss

Reclassifications out of Accumulated Other Comprehensive Loss

17. Reclassifications out of Accumulated Other Comprehensive Loss

The accumulated balances and reporting period activities for the years ended September 30, 2017, 2016 and 2015 related to reclassifications out of accumulated other comprehensive loss are summarized as follows (in millions):

	Pension Related Adjustments			Foreign Currency Translation Adjustments			Loss on Derivative Instruments			Accumulated Other Comprehensive Loss
Balances at September 30, 2014	$	(217.0	)	$	(137.8	)	$	(1.8	)	$	(356.6	)
Other comprehensive income (loss) before reclassification		5.8			(282.3	)		(13.3	)		(289.8	)
Amounts reclassified from accumulated other comprehensive loss		7.2			—			4.1			11.3

Balances at September 30, 2015	$	(204.0	)	$	(420.1	)	$	(11.0	)	$	(635.1	)

	Pension Related Adjustments			Foreign Currency Translation Adjustments			Loss on Derivative Instruments			Accumulated Other Comprehensive Loss
Balances at September 30, 2015	$	(204.0	)	$	(420.1	)	$	(11.0	)	$	(635.1	)
Other comprehensive income (loss) before reclassification		(171.5	)		(63.6	)		1.2			(233.9	)
Amounts reclassified from accumulated other comprehensive loss		6.6			—			4.8			11.4

Balances at September 30, 2016	$	(368.9	)	$	(483.7	)	$	(5.0	)	$	(857.6	)

	Pension Related Adjustments			Foreign Currency Translation Adjustments			Loss on Derivative Instruments			Accumulated Other Comprehensive Loss
Balances at September 30, 2016	$	(368.9	)	$	(483.7	)	$	(5.0	)	$	(857.6	)
Other comprehensive income (loss) before reclassification		73.8			65.3			2.3			141.4
Amounts reclassified from accumulated other comprehensive loss		13.2			—			2.3			15.5

Balances at September 30, 2017	$	(281.9	)	$	(418.4	)	$	(0.4	)	$	(700.7	)

- Definition

The entire disclosure for comprehensive income, which includes, but is not limited to, 1) the amount of income tax expense or benefit allocated to each component of other comprehensive income, including reclassification adjustments, 2) the reclassification adjustments for each classification of other comprehensive income and 3) the ending accumulated balances for each component of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e689-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=66004124&loc=SL7669619-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e640-108580

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e716-108580

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 16
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e709-108580

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e637-108580

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e681-108580

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Reclassification Adjustments
-URI http://asc.fasb.org/extlink&oid=6522872

+ Details

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Sep. 30, 2017
Commitments and Contingencies
Commitments and Contingencies	18. Commitments and Contingencies The Company records amounts representing its probable estimated liabilities relating to claims, guarantees, litigation, audits and investigations. The Company relies in part on qualified actuaries to assist it in determining the level of reserves to establish for insurance-related claims that are known and have been asserted against it, and for insurance-related claims that are believed to have been incurred based on actuarial analysis, but have not yet been reported to the Company's claims administrators as of the respective balance sheet dates. The Company includes any adjustments to such insurance reserves in its consolidated results of operations. The Company's reasonably possible loss disclosures are presented on a gross basis prior to the consideration of insurance recoveries. The Company does not record gain contingencies until they are realized. In the ordinary course of business, the Company may not be aware that it or its affiliates are under investigation and may not be aware of whether or not a known investigation has been concluded. In the ordinary course of business, the Company may enter into various arrangements providing financial or performance assurance to clients, lenders, or partners. Such arrangements include standby letters of credit, surety bonds, and corporate guarantees to support the creditworthiness or the project execution commitments of its affiliates, partnerships and joint ventures. Performance arrangements typically have various expiration dates ranging from the completion of the project contract and extending beyond contract completion in certain circumstances such as for warranties. The Company may also guarantee that a project, when complete, will achieve specified performance standards. If the project subsequently fails to meet guaranteed performance standards, the Company may incur additional costs, pay liquidated damages or be held responsible for the costs incurred by the client to achieve the required performance standards. The potential payment amount of an outstanding performance arrangement is typically the remaining cost of work to be performed by or on behalf of third parties. Generally, under joint venture arrangements, if a partner is financially unable to complete its share of the contract, the other partner(s) may be required to complete those activities. At September 30, 2017, the Company was contingently liable in the amount of approximately $503.8 million in issued standby letters of credit and $5.7 billion in issued surety bonds primarily to support project execution. In the ordinary course of business, the Company enters into various agreements providing financial or performance assurances to clients on behalf of certain unconsolidated partnerships, joint ventures and other jointly executed contracts. These agreements are entered into primarily to support the project execution commitments of these entities. In addition, in connection with the investment activities of AECOM Capital, the Company provides guarantees of certain obligations, including guarantees for completion of projects, repayment of debt, environmental indemnity obligations and other lender required guarantees. DOE Deactivation, Demolition, and Removal Project Washington Group International, an Ohio company (WGI Ohio), an affiliate of URS, executed a cost-reimbursable task order with the Department of Energy (DOE) in 2007 to provide deactivation, demolition and removal services at a New York State project site that, during 2010, experienced contamination and performance issues and remains uncompleted. In February 2011, WGI Ohio and the DOE executed a Task Order Modification that changed some cost-reimbursable contract provisions to at-risk. The Task Order Modification, including subsequent amendments, requires the DOE to pay all project costs up to $106 million, requires WGI Ohio and the DOE to equally share in all project costs incurred from $106 million to $146 million, and requires WGI Ohio to pay all project costs exceeding $146 million. Due to unanticipated requirements and permitting delays by federal and state agencies, as well as delays and related ground stabilization activities caused by Hurricane Irene in 2011, WGI Ohio has been required to perform work outside the scope of the Task Order Modification. In December 2014, WGI Ohio submitted claims against the DOE pursuant to the Contracts Disputes Acts seeking recovery of $103 million, including additional fees on changed work scope. WGI Ohio has incurred and continues to incur additional project costs outside the scope of the contract as a result of differing site and ground conditions and intends to submit additional formal claims against the DOE. Due to significant delays and uncertainties about responsibilities for the scope of remaining work, final project completion costs and other associated costs have exceeded $100 million over the contracted and claimed amounts. WGI Ohio assets and liabilities, including the value of the above costs and claims, were measured at their fair value on October 17, 2014, the date AECOM acquired WGI Ohio's parent company, see Note 3, which measurement has been reevaluated to account for developments pertaining to this matter. WGI Ohio can provide no certainty that it will recover the claims submitted against the DOE in December 2014, any future claims or any other project costs after December 2014 that WGI Ohio may be obligated to incur including the remaining project completion costs, which could have a material adverse effect on the Company's results of operations. SR-91 One of our wholly-owned subsidiaries, URS Corporation, entered into a partial fixed cost and partial time and material design agreement in 2012 with a design build contractor for a state route highway construction project in Riverside County and Orange County, California. On March 9, 2017, URS Corporation filed a $8.9 million complaint in the Superior Court of California against the design build contractor for its failure to pay for services performed under the design agreement. On April 17, 2017, the design build contractor filed a counterclaim in Superior Court alleging breaches of contract, negligent interference and professional negligence pertaining to URS Corporation's performance of design services under the design agreement, seeking purported damages of $70 million. URS Corporation cannot provide assurances that it will be successful in the recovery of the amounts owed to it under the design agreement or in its defense against the amounts alleged under the counterclaim that URS Corporation believes are without merit and that it intends to vigorously defend against. The potential range of loss in excess of any current accrual cannot be reasonably estimated at this time, primarily because the matter involves unique regulatory issues; there is substantial uncertainty regarding any alleged damages; and the matter is at a preliminary stage of litigation. New York Department of Environmental Conservation The following matter is disclosed pursuant to Regulation S-K, Item 103, Instruction 5.C pertaining to a government authority environmental claim exceeding $100,000 against an AECOM affiliate. In September 2017, AECOM USA, Inc., one of our wholly-owned subsidiaries, was advised by the New York State Department of Environmental Conservation ("DEC") of allegations that it committed environmental permit violations pursuant to the New York Environmental Conservation Law ("ECL") associated with AECOM USA, Inc.'s oversight of a water restoration project for Schoharie County which could result in substantial fines if calculated under the ECL's maximum civil penalty provisions. AECOM USA, Inc. disputes this claim and intends to continue to defend these matters vigorously; however, AECOM USA, Inc., cannot provide assurances that it will be successful in these efforts. The potential range of loss in excess of any current accrual cannot be reasonably estimated at this time, primarily because the matter involves complex and unique environmental and regulatory issues; the project site involves the oversight and involvement of various local, state and federal government agencies; substantial uncertainty regarding any alleged damages; and the preliminary stage of the government's claims.

Reportable Segments and Geographic Information

12 Months Ended

Sep. 30, 2017

Reportable Segments and Geographic Information

Reportable Segments and Geographic Information

19. Reportable Segments and Geographic Information

The Company's operations are organized into four reportable segments: Design and Consulting Services (DCS), Construction Services (CS), Management Services (MS), and AECOM Capital (ACAP). During the third quarter of fiscal 2017, operating activities of ACAP achieved a level of significance sufficient to warrant disclosure as a separate reportable segment. Prior to the third quarter of fiscal 2017, ACAP's operating results were included in the corporate segment, and comparable periods were reclassified to reflect the change. The Company's DCS reportable segment delivers planning, consulting, architectural, environmental, and engineering design services to commercial and government clients worldwide. The Company's CS reportable segment provides construction services primarily in the Americas. The Company's MS reportable segment provides program and facilities management and maintenance, training, logistics, consulting, technical assistance, and systems integration and information technology services, primarily for agencies of the U.S. government. The Company's ACAP segment invests in real estate, public-private partnership (P3) and infrastructure projects. These reportable segments are organized by the types of services provided, the differing specialized needs of the respective clients, and how the Company manages its business. The Company has aggregated various operating segments into its reportable segments based on their similar characteristics, including similar long term financial performance, the nature of services provided, internal processes for delivering those services, and types of customers.

During the first quarter of fiscal year 2017, an operation and maintenance related entity previously reported within the CS segment was realigned within the MS segment to reflect present management oversight. Accordingly, approximately $130 million and $137 million of revenue and $124 million and $130 million of cost of revenue for the years ended September 30, 2016 and 2015, respectively, were reclassified to conform to the current period presentation.

The following tables set forth summarized financial information concerning the Company's reportable segments:

Reportable Segments:	Design and Consulting Services			Construction Services			Management Services			AECOM Capital			Corporate			Total
	(in millions)
Fiscal Year Ended September 30, 2017:
Revenue	$	7,566.8		$	7,295.6		$	3,341.0		$	—		$	—		$	18,203.4
Gross profit		394.8			92.9			196.0			—			—			683.7
Equity in earnings of joint ventures		16.4			22.4			45.1			57.7			—			141.6
General and administrative expenses		—			—			—			(8.7	)		(124.7	)		(133.4	)
Acquisition and integration expenses		—			—			—			—			(38.7	)		(38.7	)
Gain on disposal activities		0.6			—			—			—			—			0.6
Operating income		411.8			115.3			241.1			49.0			(163.4	)		653.8
Segment assets		6,992.6			4,114.5			2,704.6			199.1			386.2			14,397.0
Gross profit as a % of revenue		5.2	%		1.3	%		5.9	%								3.8	%
Fiscal Year Ended September 30, 2016:
Revenue	$	7,655.8		$	6,371.1		$	3,383.9		$	—		$	—		$	17,410.8
Gross profit		382.5			25.4			234.9			—			—			642.8
Equity in earnings of joint ventures		8.9			18.2			76.9			—			—			104.0
General and administrative expenses		—			—			—			(6.0	)		(109.1	)		(115.1	)
Acquisition and integration expenses		—			—			—			—			(213.6	)		(213.6	)
Loss on disposal activities		—			(42.6	)		—			—			—			(42.6	)
Operating income		391.4			1.0			311.8			(6.0	)		(322.7	)		375.5
Segment assets		6,655.7			3,556.2			2,692.7			179.1			586.2			13,669.9
Gross profit as a % of revenue		5.0	%		0.4	%		6.9	%								3.7	%
Fiscal Year Ended September 30, 2015:
Revenue	$	7,962.9		$	6,539.3		$	3,487.7		$	—		$	—		$	17,989.9
Gross profit		299.3			35.9			200.0			—			—			535.2
Equity in earnings of joint ventures		6.6			23.0			76.6			—			—			106.2
General and administrative expenses		—			—			—			(4.3	)		(109.7	)		(114.0	)
Acquisition and integration expenses		—			—			—			—			(398.4	)		(398.4	)
Operating income		305.9			58.9			276.6			(4.3	)		(508.1	)		129.0
Segment assets		7,118.2			3,382.4			2,903.9			111.7			498.1			14,014.3
Gross profit as a % of revenue		3.8	%		0.5	%		5.7	%								3.0	%

Geographic Information:

	Fiscal Year Ended
	September 30, 2017				September 30, 2016				September 30, 2015
	Revenue		Long-Lived Assets		Revenue		Long-Lived Assets		Revenue		Long-Lived Assets
	(in millions)
United States	$	13,042.6		4,779.0	$	12,567.0		4,763.9	$	12,599.6		4,852.5
Asia Pacific		1,352.7		382.9		1,278.3		394.0		1,385.3		426.4
Canada		1,159.9		600.4		866.5		615.7		1,308.3		641.0
Europe		1,869.9		1,362.8		1,904.2		1,368.4		1,796.9		1,496.2
Other foreign countries		778.3		418.3		794.8		412.5		899.8		352.1

Total	$	18,203.4		7,543.4	$	17,410.8		7,554.5	$	17,989.9		7,768.2

The Company attributes revenue by geography based on the external customer's country of origin. Long-lived assets consist of noncurrent assets excluding deferred tax assets.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8981-108599

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e9038-108599

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8971-108599

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8595-108599

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8380-108599

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8933-108599

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 26
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8844-108599

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 35
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8984-108599

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e9031-108599

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e9054-108599

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8538-108599

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 29
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8864-108599

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8924-108599

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8906-108599

+ Details

Major Clients	12 Months Ended
Major Clients	Sep. 30, 2017
Major Clients
Major Clients	20. Major Clients Other than the U.S. federal government, no single client accounted for 10% or more of the Company's revenue in any of the past five fiscal years. Approximately 22%, 23%, and 24% of the Company's revenue was derived through direct contracts with agencies of the U.S. federal government in the years ended September 30, 2017, 2016 and 2015, respectively. One of these contracts accounted for approximately 3%, 3%, and 2% of the Company's revenue in the years ended September 30, 2017, 2016 and 2015, respectively.

Quarterly Financial Information-Unaudited

12 Months Ended

Sep. 30, 2017

Quarterly Financial Information-Unaudited

Quarterly Financial Information-Unaudited

21. Quarterly Financial Information—Unaudited

In the opinion of management, the following unaudited quarterly data reflects all adjustments necessary for a fair statement of the results of operations. All such adjustments are of a normal recurring nature.

Fiscal Year 2017:	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
	(in millions, except per share data)
Revenue	$	4,358.3		$	4,427.2		$	4,561.5		$	4,856.4
Cost of revenue		4,188.3			4,258.8			4,386.3			4,686.3

Gross profit		170.0			168.4			175.2			170.1
Equity in earnings of joint ventures		21.4			21.8			66.5			31.9
General and administrative expenses		(32.6	)		(29.9	)		(34.0	)		(36.9	)
Acquisition and integration expenses		(15.4	)		(20.0	)		—			(3.3	)
Gain on disposal activities		—			0.6			—			—

Income from operations		143.4			140.9			207.7			161.8
Other income		0.8			1.3			2.1			2.5
Interest expense		(53.6	)		(61.8	)		(61.6	)		(54.3	)

Income before income tax expense		90.6			80.4			148.2			110.0
Income tax expense (benefit)		24.8			(35.4	)		12.1			6.2

Net income		65.8			115.8			136.1			103.8
Noncontrolling interest in income of consolidated subsidiaries, net of tax		(18.6	)		(13.4	)		(34.8	)		(15.3	)

Net income attributable to AECOM	$	47.2		$	102.4		$	101.3		$	88.5


Net income attributable to AECOM per share:
Basic	$	0.31		$	0.66		$	0.65		$	0.56
Diluted	$	0.30		$	0.65		$	0.64		$	0.55
Weighted average common shares outstanding:
Basic		154.3			155.4			155.8			157.5
Diluted		158.0			158.7			158.8			161.1

Fiscal Year 2016:	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
	(in millions, except per share data)
Revenue	$	4,297.7		$	4,381.2		$	4,408.8		$	4,323.1
Cost of revenue		4,156.8			4,197.8			4,237.5			4,175.9

Gross profit		140.9			183.4			171.3			147.2
Equity in earnings of joint ventures		25.2			39.1			18.5			21.2
General and administrative expenses		(28.7	)		(29.5	)		(28.7	)		(28.2	)
Acquisition and integration expenses		(41.0	)		(50.7	)		(50.7	)		(71.2	)
Loss on disposal activities		(41.0	)		(1.6	)		—			—

Income from operations		55.4			140.7			110.4			69.0
Other income		3.0			0.8			1.5			2.9
Interest expense		(59.5	)		(62.7	)		(62.6	)		(73.3	)

(Loss) / income before income tax expense		(1.1	)		78.8			49.3			(1.4	)
Income tax (benefit) expense		(0.7	)		12.2			(35.1	)		(14.3	)

Net (loss) / income		(0.4	)		66.6			84.4			12.9
Noncontrolling interest in income of consolidated subsidiaries, net of tax		(20.0	)		(24.7	)		(17.0	)		(5.7	)

Net (loss) / income attributable to AECOM	$	(20.4	)	$	41.9		$	67.4		$	7.2


Net (loss) / income attributable to AECOM per share:
Basic	$	(0.13	)	$	0.27		$	0.44		$	0.05
Diluted	$	(0.13	)	$	0.27		$	0.43		$	0.05
Weighted average common shares outstanding:
Basic		153.6			154.3			154.9			156.3
Diluted		153.6			155.4			156.2			157.9

Condensed Consolidating Financial Information

12 Months Ended

Sep. 30, 2017

Condensed Consolidating Financial Information

Condensed Consolidating Financial Information

22. Condensed Consolidating Financial Information

In connection with the registration of the Company's 2014 Senior Notes that were declared effective by the SEC on September 29, 2015, AECOM became subject to the requirements of Rule 3-10 of Regulation S-X regarding financial statements of guarantors and issuers of guaranteed securities. Both the 2014 Senior Notes and the 2017 Senior Notes are fully and unconditionally guaranteed on a joint and several basis by certain of AECOM's directly and indirectly 100% owned subsidiaries (the Subsidiary Guarantors). Other than customary restrictions imposed by applicable statutes, there are no restrictions on the ability of the Subsidiary Guarantors to transfer funds to AECOM in the form of cash dividends, loans or advances.

The following condensed consolidating financial information, which is presented for AECOM, the Subsidiary Guarantors on a combined basis and AECOM's non-guarantor subsidiaries on a combined basis, is provided to satisfy the disclosure requirements of Rule 3-10 of Regulation S-X.

Condensed Consolidating Balance Sheets
(in millions)
September 30, 2017

	Parent		Guarantor Subsidiaries		Non- Guarantor Subsidiaries		Eliminations			Total
ASSETS
CURRENT ASSETS:
Total cash and cash equivalents	$	32.6	$	251.6	$	518.2	$	—		$	802.4
Accounts receivable—net		—		2,159.2		2,968.5		—			5,127.7
Intercompany receivable		723.6		90.9		181.4		(995.9	)		—
Prepaid expenses and other current assets		67.5		338.4		290.8		—			696.7
Income taxes receivable		4.3		—		51.1		—			55.4

TOTAL CURRENT ASSETS		828.0		2,840.1		4,010.0		(995.9	)		6,682.2
PROPERTY AND EQUIPMENT—NET		160.2		207.1		254.1		—			621.4
DEFERRED TAX ASSETS—NET		239.7		55.2		171.0		(294.6	)		171.3
INVESTMENTS IN CONSOLIDATED JOINT VENTURES		6,606.2		2,865.0		—		(9,471.2	)		—
INVESTMENTS IN UNCONSOLIDATED JOINT VENTURES		7.2		50.3		306.7		—			364.2
GOODWILL		—		3,318.6		2,674.3		—			5,992.9
INTANGIBLE ASSETS—NET		—		271.6		143.5		—			415.1
OTHER NON-CURRENT ASSETS		8.7		17.6		123.6		—			149.9

TOTAL ASSETS	$	7,850.0	$	9,625.5	$	7,683.2	$	(10,761.7	)	$	14,397.0


LIABILITIES AND STOCKHOLDERS' EQUITY
CURRENT LIABILITIES:
Short-term debt	$	1.1	$	—	$	0.1	$	—		$	1.2
Accounts payable		33.8		1,023.7		1,192.4		—			2,249.9
Accrued expenses and other current liabilities		92.2		1,112.9		1,040.4		—			2,245.5
Accrued taxes payable		—		—		38.2		—			38.2
Intercompany payable		149.2		787.5		161.4		(1,098.1	)		—
Billings in excess of costs on uncompleted contracts		3.4		313.1		586.3		—			902.8
Current portion of long-term debt		110.9		14.9		15.0		—			140.8

TOTAL CURRENT LIABILITIES		390.6		3,252.1		3,033.8		(1,098.1	)		5,578.4
OTHER LONG-TERM LIABILITIES		102.3		285.7		493.3		—			881.3
DEFERRED TAX LIABILITY—NET		—		—		315.1		(294.6	)		20.5
NOTE PAYABLE INTERCOMPANY—NON CURRENT		0.1		—		467.2		(467.3	)		—
LONG-TERM DEBT		3,366.9		281.6		53.6		—			3,702.1

TOTAL LIABILITIES		3,859.9		3,819.4		4,363.0		(1,860.0	)		10,182.3
TOTAL AECOM STOCKHOLDERS' EQUITY		3,990.1		5,806.1		3,101.6		(8,901.7	)		3,996.1
Noncontrolling interests		—		—		218.6		—			218.6

TOTAL STOCKHOLDERS' EQUITY		3,990.1		5,806.1		3,320.2		(8,901.7	)		4,214.7

TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$	7,850.0	$	9,625.5	$	7,683.2	$	(10,761.7	)	$	14,397.0

Condensed Consolidating Balance Sheets
(in millions)
September 30, 2016

	Parent		Guarantor Subsidiaries		Non- Guarantor Subsidiaries		Eliminations			Total
ASSETS
CURRENT ASSETS:
Total cash and cash equivalents	$	1.8	$	183.7	$	506.6	$	—		$	692.1
Accounts receivable—net		—		2,034.0		2,497.5		—			4,531.5
Intercompany receivable		760.7		151.7		152.0		(1,064.4	)		—
Prepaid expenses and other current assets		98.7		336.2		295.2		—			730.1
Income taxes receivable		28.7		—		18.4		—			47.1

TOTAL CURRENT ASSETS		889.9		2,705.6		3,469.7		(1,064.4	)		6,000.8
PROPERTY AND EQUIPMENT—NET		169.3		236.5		239.2		—			645.0
DEFERRED TAX ASSETS—NET		265.2		—		129.8		(223.5	)		171.5
INVESTMENTS IN CONSOLIDATED SUBSIDIARIES		6,031.7		2,681.5		—		(8,713.2	)		—
INVESTMENTS IN UNCONSOLIDATED JOINT VENTURES		0.7		48.6		281.2		—			330.5
GOODWILL		—		3,286.6		2,537.2		—			5,823.8
INTANGIBLE ASSETS—NET		—		334.0		145.4		—			479.4
OTHER NON-CURRENT ASSETS		8.2		71.5		139.2		—			218.9

TOTAL ASSETS	$	7,365.0	$	9,364.3	$	6,941.7	$	(10,001.1	)	$	13,669.9


LIABILITIES AND STOCKHOLDERS' EQUITY
CURRENT LIABILITIES:
Short-term debt	$	3.1	$	7.3	$	15.9	$	—		$	26.3
Accounts payable		45.8		907.0		958.1		—			1,910.9
Accrued expenses and other current liabilities		201.2		1,137.1		1,046.5		—			2,384.8
Accrued taxes payable		—		—		10.8		—			10.8
Intercompany payable		114.1		857.9		208.8		(1,180.8	)		—
Billings in excess of costs on uncompleted contracts		—		237.5		394.4		—			631.9
Current portion of long-term debt		108.2		222.1		9.7		—			340.0

TOTAL CURRENT LIABILITIES		472.4		3,368.9		2,644.2		(1,180.8	)		5,304.7
OTHER LONG-TERM LIABILITIES		115.7		349.3		632.4		—			1,097.4
DEFERRED TAX LIABILITY—NET		—		236.6		—		(223.5	)		13.1
NOTE PAYABLE INTERCOMPANY—NON CURRENT		—		—		563.5		(563.5	)		—
LONG-TERM DEBT		3,411.2		273.4		17.6		—			3,702.2

TOTAL LIABILITIES		3,999.3		4,228.2		3,857.7		(1,967.8	)		10,117.4
TOTAL AECOM STOCKHOLDERS' EQUITY		3,365.7		5,136.1		2,898.4		(8,033.3	)		3,366.9
Noncontrolling interests		—		—		185.6		—			185.6

TOTAL STOCKHOLDERS' EQUITY		3,365.7		5,136.1		3,084.0		(8,033.3	)		3,552.5

TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$	7,365.0	$	9,364.3	$	6,941.7	$	(10,001.1	)	$	13,669.9

Condensed Consolidating Statements of Operations
(in millions)

	For the Fiscal Year Ended September 30, 2017
	Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Total
Revenue	$	—		$	9,367.1		$	8,905.0		$	(68.7	)	$	18,203.4
Cost of revenue		—			9,000.3			8,588.1			(68.7	)		17,519.7

Gross profit		—			366.8			316.9			—			683.7
Equity in earnings from subsidiaries		439.3			217.2			—			(656.5	)		—
Equity in earnings of joint ventures		—			25.4			116.2			—			141.6
General and administrative expenses		(124.7	)		—			(8.7	)		—			(133.4	)
Acquisition and integration expenses		(38.7	)		—			—			—			(38.7	)
Gain on disposal activities		—			—			0.6			—			0.6

Income from operations		275.9			609.4			425.0			(656.5	)		653.8
Other income		2.2			31.7			9.3			(36.5	)		6.7
Interest expense		(203.7	)		(26.5	)		(37.6	)		36.5			(231.3	)

Income before income tax (benefit) expense		74.4			614.6			396.7			(656.5	)		429.2
Income tax (benefit) expense		(264.9	)		175.8			65.1			31.7			7.7

Net income		339.3			438.8			331.6			(688.2	)		421.5
Noncontrolling interests in income of consolidated subsidiaries, net of tax		—			—			(82.1	)		—			(82.1	)

Net income attributable to AECOM	$	339.3		$	438.8		$	249.5		$	(688.2	)	$	339.4

	For the Fiscal Year Ended September 30, 2016
	Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Total
Revenue	$	—		$	9,227.5		$	8,265.3		$	(82.0	)	$	17,410.8
Cost of revenue		—			8,909.4			7,940.6			(82.0	)		16,768.0

Gross profit		—			318.1			324.7			—			642.8
Equity in earnings from subsidiaries		437.4			243.6			—			(681.0	)		—
Equity in earnings of joint ventures		—			27.3			76.7			—			104.0
General and administrative expenses		(114.0	)		(1.1	)		—			—			(115.1	)
Acquisition and integration expenses		(213.6	)		—			—			—			(213.6	)
Loss on disposal activities		—			—			(42.6	)		—			(42.6	)

Income from operations		109.8			587.9			358.8			(681.0	)		375.5
Other income		0.8			34.7			12.7			(40.0	)		8.2
Interest expense		(231.7	)		(23.6	)		(42.8	)		40.0			(258.1	)

Income (loss) before income tax expense		(121.1	)		599.0			328.7			(681.0	)		125.6
Income tax (benefit) expense		(217.3	)		114.3			27.8			37.3			(37.9	)

Net income		96.2			484.7			300.9			(718.3	)		163.5
Noncontrolling interests in income of consolidated subsidiaries, net of tax		—			—			(67.4	)		—			(67.4	)

Net income attributable to AECOM	$	96.2		$	484.7		$	233.5		$	(718.3	)	$	96.1

	For the Fiscal Year Ended September 30, 2015
	Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Total
Revenue	$	—		$	8,749.5		$	9,463.6		$	(223.2	)	$	17,989.9
Cost of revenue		—			8,486.4			9,191.5			(223.2	)		17,454.7

Gross profit		—			263.1			272.1			—			535.2
Equity in earnings from subsidiaries		321.3			198.9			—			(520.2	)		—
Equity in earnings of joint ventures		—			20.0			86.2			—			106.2
General and administrative expenses		(112.2	)		(1.8	)		—			—			(114.0	)
Acquisition and integration expenses		(346.9	)		(51.5	)		—			—			(398.4	)

(Loss) income from operations		(137.8	)		428.7			358.3			(520.2	)		129.0
Other income		5.1			34.9			14.7			(35.6	)		19.1
Interest expense		(275.4	)		(20.4	)		(39.4	)		35.6			(299.6	)

(Loss) income before income tax expense		(408.1	)		443.2			333.6			(520.2	)		(151.5	)
Income tax (benefit) expense		(253.3	)		66.7			61.0			45.3			(80.3	)

Net (loss) income		(154.8	)		376.5			272.6			(565.5	)		(71.2	)
Noncontrolling interests in income of consolidated subsidiaries, net of tax		—			—			(83.6	)		—			(83.6	)

Net (loss) income attributable to AECOM	$	(154.8	)	$	376.5		$	189.0		$	(565.5	)	$	(154.8	)

Consolidating Statements of Comprehensive Income (Loss)
(in millions)

	For the Fiscal Year Ended September 30, 2017
	Parent		Guarantor Subsidiaries		Non-Guarantor Subsidiaries			Eliminations			Total
Net income	$	339.3	$	438.8	$	331.6		$	(688.2	)	$	421.5
Other comprehensive income (loss), net of tax:
Net unrealized gain (loss) on derivatives, net of tax		4.9		—		(0.3	)		—			4.6
Foreign currency translation adjustments		—		—		65.4			—			65.4
Pension adjustments, net of tax		7.1		13.8		66.1			—			87.0

Other comprehensive income, net of tax		12.0		13.8		131.2			—			157.0

Comprehensive income, net of tax		351.3		452.6		462.8			(688.2	)		578.5
Noncontrolling interests in comprehensive income of consolidated subsidiaries, net of tax		—		—		(82.2	)		—			(82.2	)

Comprehensive income attributable to AECOM, net of tax	$	351.3	$	452.6	$	380.6		$	(688.2	)	$	496.3

	For the Fiscal Year Ended September 30, 2016
	Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Total
Net income	$	96.2		$	484.7		$	300.9		$	(718.3	)	$	163.5
Other comprehensive income (loss), net of tax:
Net unrealized gain on derivatives, net of tax		2.6			—			3.4			—			6.0
Foreign currency translation adjustments		—			—			(65.3	)		—			(65.3	)
Pension adjustments, net of tax		(3.3	)		(14.9	)		(146.7	)		—			(164.9	)

Other comprehensive loss, net of tax		(0.7	)		(14.9	)		(208.6	)		—			(224.2	)

Comprehensive income (loss), net of tax		95.5			469.8			92.3			(718.3	)		(60.7	)
Noncontrolling interests in comprehensive income of consolidated subsidiaries, net of tax		—			—			(65.7	)		—			(65.7	)

Comprehensive income (loss) attributable to AECOM, net of tax	$	95.5		$	469.8		$	26.6		$	(718.3	)	$	(126.4	)

	For the Fiscal Year Ended September 30, 2015
	Parent			Guarantor Subsidiaries		Non-Guarantor Subsidiaries			Eliminations			Total
Net (loss) income	$	(154.8	)	$	376.5	$	272.6		$	(565.5	)	$	(71.2	)
Other comprehensive income (loss), net of tax:
Net unrealized loss on derivatives, net of tax		(6.1	)		—		(3.1	)		—			(9.2	)
Foreign currency translation adjustments		—			—		(285.6	)		—			(285.6	)
Pension adjustments, net of tax		1.8			6.4		4.8			—			13.0

Other comprehensive (loss) income, net of tax		(4.3	)		6.4		(283.9	)		—			(281.8	)

Comprehensive (loss) income, net of tax		(159.1	)		382.9		(11.3	)		(565.5	)		(353.0	)
Noncontrolling interests in comprehensive income of consolidated subsidiaries, net of tax		—			—		(80.3	)		—			(80.3	)

Comprehensive (loss) income attributable to AECOM, net of tax	$	(159.1	)	$	382.9	$	(91.6	)	$	(565.5	)	$	(433.3	)

Condensed Consolidating Statements of Cash Flows
(in millions)

	For the Fiscal Year Ended September 30, 2017
	Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Total
CASH FLOWS FROM OPERATING ACTIVITIES	$	(5.9	)	$	691.2		$	11.4		$	—		$	696.7
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments for business acquisitions, net of cash acquired		—			—			(103.1	)		—			(103.1	)
Proceeds from disposal of business, net of cash disposed		—			—			2.2			—			2.2
Net investment in unconsolidated joint ventures		—			(2.6	)		(21.7	)		—			(24.3	)
Net purchases of investments		—			—			0.9			—			0.9
Payments for capital expenditures, net of disposals		(21.7	)		(29.3	)		(27.4	)		—			(78.4	)
Net investment in intercompany notes		(4.6	)		102.8			12.2			(110.4	)		—
Other intercompany investing activities		139.0			(221.0	)		—			82.0			—

Net cash provided by (used in) investing activities		112.7			(150.1	)		(136.9	)		(28.4	)		(202.7	)

CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from borrowings under credit agreements		5,903.5			13.1			36.6			—			5,953.2
Repayments of borrowings under credit agreements		(6,956.3	)		(51.1	)		(64.2	)		—			(7,071.6	)
Issuance of unsecured senior notes		1,000.0			—			—			—			1,000.0
Redemption of unsecured senior notes		—			(179.2	)		—			—			(179.2	)
Cash paid for debt and equity issuance costs		(13.0	)		—			—			—			(13.0	)
Proceeds from issuance of common stock		30.1			—			—			—			30.1
Proceeds from exercise of stock options		4.9			—			—			—			4.9
Payments to repurchase common stock		(25.1	)		—			—			—			(25.1	)
Net distributions to noncontrolling interests		—			—			(59.0	)		—			(59.0	)
Other financing activities		(24.1	)		(38.3	)		35.6			—			(26.8	)
Net borrowings (repayments) on intercompany notes		4.0			(16.3	)		(98.1	)		110.4			—
Other intercompany financing activities		—			(201.4	)		283.4			(82.0	)		—

Net cash (used in) provided by financing activities		(76.0	)		(473.2	)		134.3			28.4			(386.5	)

EFFECT OF EXCHANGE RATE CHANGES ON CASH		—			—			2.8			—			2.8
NET INCREASE IN CASH AND CASH EQUIVALENTS		30.8			67.9			11.6			—			110.3
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR		1.8			183.7			506.6			—			692.1

CASH AND CASH EQUIVALENTS AT END OF YEAR	$	32.6		$	251.6		$	518.2		$	—		$	802.4

	For the Fiscal Year Ended September 30, 2016
	Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Total
CASH FLOWS FROM OPERATING ACTIVITIES	$	(273.6	)	$	623.7		$	464.1		$	—		$	814.2
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments for business acquisitions, net of cash acquired		—			(1.0	)		(4.5	)		—			(5.5	)
Proceeds from disposal of businesses and property		—			—			39.7			—			39.7
Net investment in unconsolidated joint ventures		—			(3.9	)		(67.6	)		—			(71.5	)
Net sales of investments		—			—			11.5			—			11.5
Payments for capital expenditures, net of disposals		(82.0	)		(58.7	)		3.9			—			(136.8	)
Net receipts from (investment in) intercompany notes		5.3			176.1			(13.5	)		(167.9	)		—
Other intercompany investing activities		791.2			140.3			—			(931.5	)		—

Net cash provided by (used in) investing activities		714.5			252.8			(30.5	)		(1,099.4	)		(162.6	)

CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from borrowings under credit agreements		4,673.0			17.6			15.6			—			4,706.2
Repayments of borrowings under credit agreements		(5,124.1	)		(22.8	)		(53.1	)		—			(5,200.0	)
Cash paid for debt and equity issuance costs		(10.4	)		—			—			—			(10.4	)
Proceeds from issuance of common stock		28.2			—			—			—			28.2
Proceeds from exercise of stock options		9.9			—			—			—			9.9
Payments to repurchase common stock		(25.9	)		—			—			—			(25.9	)
Excess tax benefit from share-based payment		—			—			—			—			—
Net distributions to noncontrolling interests		—			—			(103.2	)		—			(103.2	)
Other financing activities		7.9			(4.5	)		(46.3	)		—			(42.9	)
Net borrowings (repayments) on intercompany notes		1.0			12.5			(181.4	)		167.9			—
Other intercompany financing activities		—			(858.1	)		(73.4	)		931.5			—

Net cash used in financing activities		(440.4	)		(855.3	)		(441.8	)		1,099.4			(638.1	)

EFFECT OF EXCHANGE RATE CHANGES ON CASH		—			—			(5.3	)		—			(5.3	)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS		0.5			21.2			(13.5	)		—			8.2
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR		1.3			162.5			520.1			—			683.9

CASH AND CASH EQUIVALENTS AT END OF YEAR	$	1.8		$	183.7		$	506.6		$	—		$	692.1

	For the Fiscal Year Ended September 30, 2015
	Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Total
CASH FLOWS FROM OPERATING ACTIVITIES	$	(551.2	)	$	816.9		$	498.7		$	—		$	764.4
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments for business acquisitions, net of cash acquired		(3,564.2	)		109.2			161.7			—			(3,293.3	)
Proceeds from disposal of businesses and property		9.5			5.6			—			—			15.1
Net investment in unconsolidated joint ventures		—			(4.0	)		(28.7	)		—			(32.7	)
Sales (purchases) of investments		37.3			—			(2.7	)		—			34.6
Payments for capital expenditures, net of disposals		(51.9	)		(15.8	)		(1.7	)		—			(69.4	)
Receipts from intercompany notes receivable		95.6			128.6			—			(224.2	)		—
Other intercompany investing activities		1,085.8			160.9			—			(1,246.7	)		—

Net cash (used in) provided by investing activities		(2,387.9	)		384.5			128.6			(1,470.9	)		(3,345.7	)

CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from borrowings under credit agreements		6,464.6			29.9			87.2			—			6,581.7
Repayments of borrowings under credit agreements		(5,031.9	)		(31.2	)		(95.2	)		—			(5,158.3	)
Issuance of unsecured senior notes		1,600.0			—			—			—			1,600.0
Prepayment penalty on Unsecured Senior Notes		(55.6	)		—			—			—			(55.6	)
Cash paid for debt and equity issuance costs		(89.6	)		—			—			—			(89.6	)
Proceeds from issuance of common stock		25.6			—			—			—			25.6
Proceeds from exercise of stock options		11.1			—			—			—			11.1
Payments to repurchase common stock		(23.1	)		—			—			—			(23.1	)
Excess tax benefit from share-based payment		3.6			—			—			—			3.6
Net distributions to noncontrolling interests		—			—			(144.3	)		—			(144.3	)
Other financing activities		2.3			(4.1	)		(29.5	)		—			(31.3	)
Intercompany notes repayments		—			—			(224.2	)		224.2			—
Other intercompany financing activities		—			(1,119.3	)		(127.4	)		1,246.7			—

Net cash provided by (used in) financing activities		2,907.0			(1,124.7	)		(533.4	)		1,470.9			2,719.8

EFFECT OF EXCHANGE RATE CHANGES ON CASH		—			—			(28.8	)		—			(28.8	)
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS		(32.1	)		76.7			65.1			—			109.7
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR		33.4			85.8			455.0			—			574.2

CASH AND CASH EQUIVALENTS AT END OF YEAR	$	1.3		$	162.5		$	520.1		$	—		$	683.9

Schedule II: Valuation and Qualifying Accounts

12 Months Ended

Sep. 30, 2017

Schedule II: Valuation and Qualifying Accounts

Schedule II: Valuation and Qualifying Accounts

(amounts in millions)

	Balance at Beginning of Year		Additions Charged to Cost of Revenue		Deductions(a)			Other and Foreign Exchange Impact			Balance at the End of the Year
Allowance for Doubtful Accounts
Fiscal Year 2017	$	60.4	$	13.1	$	(20.7	)	$	(0.6	)	$	52.2
Fiscal Year 2016	$	64.1	$	16.4	$	(20.5	)	$	0.4		$	60.4
Fiscal Year 2015	$	72.1	$	26.9	$	(31.2	)	$	(3.7	)	$	64.1

(a)	Primarily relates to accounts written-off and recoveries

Significant Accounting Policies (Policies)

12 Months Ended

Sep. 30, 2017

Significant Accounting Policies

Fiscal Year

Use of Estimates

Principles of Consolidation and Presentation

Revenue Recognition

Cost-Reimbursable Contracts

Cost-reimbursable contracts consists of two similar contract types: (1) cost-plus contracts and (2) time-and-materials price contracts.

Cost-Plus Contracts. The Company enters into two major types of cost-plus contracts:

Time-and-Materials Price Contracts

Guaranteed Maximum Price Contracts

Fixed-Price Contracts

During the years ended September 30, 2017, 2016 and 2015, the types of contracts comprising the Company's revenue were as follows:

	Fiscal Year Ended
	September 30, 2017			September 30, 2016			September 30, 2015
Cost reimbursable		48	%		53	%		57	%
Guaranteed maximum price		23	%		15	%		15	%
Fixed price		29	%		32	%		28	%

Cost reimbursable contracts include cost-plus and time-and-materials price contracts.

Government Contract Matters

Cash and Cash Equivalents

Cash and Cash Equivalents—The Company's cash equivalents include highly liquid investments which have an initial maturity of three months or less.

Allowance for Doubtful Accounts

•Client type—federal or state and local government or commercial client;

•Historical contract performance;

•Historical collection and delinquency trends;

•Client credit worthiness; and

•General economic conditions.

Derivative Financial Instruments

Derivative Financial Instruments—The Company accounts for its derivative instruments as either assets or liabilities and carries them at fair value.

Derivatives that do not qualify as hedges are adjusted to fair value through current income.

Fair Value of Financial Instruments

Property and Equipment

Long-lived Assets

Goodwill and Acquired Intangible Assets

Pension Plans

Insurance Reserves

Foreign Currency Translation

Noncontrolling Interests

Income Taxes

Significant Accounting Policies (Tables)

12 Months Ended

Sep. 30, 2017

Significant Accounting Policies

Schedule of types of contracts comprising Company's revenues

	Fiscal Year Ended
	September 30, 2017			September 30, 2016			September 30, 2015
Cost reimbursable		48	%		53	%		57	%
Guaranteed maximum price		23	%		15	%		15	%
Fixed price		29	%		32	%		28	%

Business Acquisitions, Goodwill and Intangible Assets (Tables)

12 Months Ended

Sep. 30, 2017

Business Acquisitions, Goodwill and Intangible Assets

Schedule of acquisition and integration expenses

	Fiscal Year Ended
	Sept 30, 2017		Sept 30, 2016
	(in millions)
Severance and personnel costs	$	32.0	$	23.4
Professional service, real estate-related, and other expenses		6.7		190.2

Total	$	38.7	$	213.6

Schedule of acquired intangible assets from acquisitions

	Fiscal Year Ended Sept 30, 2017
	(in millions)
Cash acquired	$	28.0
Other current assets		118.3
Identifiable intangible assets:
Customer relationships, contracts and backlog		24.5
Trademark / tradename		1.8

Total intangible assets	$	26.3

Goodwill		127.1
Other non-current assets		29.5
Current liabilities		(123.1	)
Non-current liabilities		(29.3	)
Noncontrolling interest		(10.2	)

Net assets acquired	$	166.6

Schedule of consideration for acquisitions

	Fiscal Year Ended Sept 30, 2017
	(in millions)
Cash paid	$	130.0
Equity issued		36.6

Total consideration	$	166.6

Schedule of changes in the carrying value of goodwill by reportable segment

	Fiscal Year 2017
	September 30, 2016		Acquisitions		Disposed			Foreign Exchange Impact		September 30, 2017
	(in millions)
Design and Consulting Services	$	3,198.2	$	3.8	$	(1.8	)	$	18.7	$	3,218.9
Construction Services		915.2		123.3		—			11.4		1,049.9
Management Services		1,710.4		—		—			13.7		1,724.1

Total	$	5,823.8	$	127.1	$	(1.8	)	$	43.8	$	5,992.9

	Fiscal Year 2016
	September 30, 2015		Post- Acquisition Adjustments		Disposed			Foreign Exchange Impact			September 30, 2016
	(in millions)
Design and Consulting Services	$	3,163.3	$	26.7	$	—		$	8.2		$	3,198.2
Construction Services		918.5		8.7		(11.3	)		(0.7	)		915.2
Management Services		1,738.9		4.0		—			(32.5	)		1,710.4

Total	$	5,820.7	$	39.4	$	(11.3	)	$	(25.0	)	$	5,823.8

Schedule of finite-lived intangible assets by major class

	September 30, 2017							September 30, 2016
	Gross Amount		Accumulated Amortization			Intangible Assets, Net		Gross Amount		Accumulated Amortization			Intangible Assets, Net		Amortization Period (years)
	(in millions)
Backlog and customer relationships	$	1,283.6	$	(870.2	)	$	413.4	$	1,247.1	$	(767.7	)	$	479.4	1 - 11
Trademark / tradename		18.3		(16.6	)		1.7		16.4		(16.4	)		—	0.3 - 2

Total	$	1,301.9	$	(886.8	)	$	415.1	$	1,263.5	$	(784.1	)	$	479.4

Schedule of estimated future amortization expense of intangible assets

Fiscal Year	(in millions)
2018	$	91.7
2019		84.5
2020		70.5
2021		59.5
2022		46.3
Thereafter		62.6

Total	$	415.1

Accounts Receivable - Net (Tables)

12 Months Ended

Sep. 30, 2017

Accounts Receivable - Net

Schedule of net accounts receivable

	Fiscal Year Ended
	September 30, 2017			September 30, 2016
	(in millions)
Billed	$	2,317.8		$	2,267.6
Unbilled		2,293.5			1,890.2
Contract retentions		568.6			434.1

Total accounts receivable—gross		5,179.9			4,591.9
Allowance for doubtful accounts		(52.2	)		(60.4	)

Total accounts receivable—net	$	5,127.7		$	4,531.5

Property and Equipment (Tables)

12 Months Ended

Sep. 30, 2017

Property and Equipment

Schedule of property and equipment, at cost

	Fiscal Year Ended
	September 30, 2017			September 30, 2016			Useful Lives (years)
	(in millions)
Building and land	$	63.6		$	57.9		10 - 45
Leasehold improvements		404.6			381.4		1 - 20
Computer systems and equipment		694.6			652.0		3 - 12
Furniture and fixtures		135.9			129.7		3 - 10

Total		1,298.7			1,221.0
Accumulated depreciation and amortization		(677.3	)		(576.0	)

Property and equipment, net	$	621.4		$	645.0

Joint Ventures and Variable Interest Entities (Tables)

12 Months Ended

Sep. 30, 2017

Joint Ventures and Variable Interest Entities

Summary of financial information of the consolidated joint ventures

	September 30, 2017		September 30, 2016
	(in millions)
Current assets	$	832.1	$	684.1
Non-current assets		188.8		230.8

Total assets	$	1,020.9	$	914.9


Current liabilities	$	524.9	$	407.4
Non-current liabilities		12.4		12.4

Total liabilities		537.3		419.8
Total AECOM equity		274.7		318.0
Noncontrolling interests		208.9		177.1

Total owners' equity		483.6		495.1

Total liabilities and owners' equity	$	1,020.9	$	914.9

Summary of financial information of the unconsolidated joint ventures, as derived from their unaudited financial statements

	September 30, 2017		September 30, 2016
	(in millions)
Current assets	$	1,912.2	$	1,407.0
Non-current assets		749.8		499.4

Total assets	$	2,662.0	$	1,906.4


Current liabilities	$	1,570.2	$	977.3
Non-current liabilities		185.1		146.2

Total liabilities		1,755.3		1,123.5
Joint ventures' equity		906.7		782.9

Total liabilities and joint ventures' equity	$	2,662.0	$	1,906.4


AECOM's investment in joint ventures	$	364.2	$	330.5

	Twelve Months Ended
	September 30, 2017		September 30, 2016
	(in millions)
Revenue	$	5,561.8	$	4,871.8
Cost of revenue		5,305.5		4,618.3

Gross profit	$	256.3	$	253.5

Net income	$	244.8	$	233.9

Summary of AECOM's equity in earnings of unconsolidated joint ventures

	Fiscal Year Ended
	September 30, 2017		September 30, 2016		September 30, 2015
	(in millions)
Pass through joint ventures	$	36.6	$	21.9	$	26.2
Other joint ventures		105.0		82.1		80.0

Total	$	141.6	$	104.0	$	106.2

Pension Benefit Obligations (Tables)

12 Months Ended

Sep. 30, 2017

Pension Benefit Obligations

Reconciliations of the changes in the U.S. and international plans' benefit obligations

	Fiscal Year Ended
	September 30, 2017						September 30, 2016						September 30, 2015
	U.S.			Int'l			U.S.			Int'l			U.S.			Int'l
	(in millions)
Change in benefit obligation:
Benefit obligation at beginning of year	$	720.0		$	1,406.2		$	718.2		$	1,239.2		$	217.0		$	676.6
Service cost		4.3			1.3			4.3			1.0			6.8			1.1
Participant contributions		0.1			0.4			0.1			0.5			0.4			0.5
Interest cost		19.2			28.3			22.0			39.2			28.2			47.1
Benefits and expenses paid		(37.9	)		(48.3	)		(37.4	)		(41.9	)		(33.9	)		(41.0	)
Actuarial (gain) loss		(22.7	)		(98.6	)		52.3			377.1			(41.0	)		10.6
Plan settlements		—			—			(32.9	)		(0.7	)		(20.1	)		(2.5	)
Plan amendments		—			—			0.2			—			—			—
Plan curtailments		—			—			(6.8	)		—			—			—
Net transfer in/(out)/acquisitions		—			—			—			—			560.8			618.6
Foreign currency translation loss (gain)		—			44.2			—			(208.2	)		—			(71.8	)

Benefit obligation at end of year	$	683.0		$	1,333.5		$	720.0		$	1,406.2		$	718.2		$	1,239.2

Reconciliations of the changes in the fair value of assets

	Fiscal Year Ended
	September 30, 2017						September 30, 2016						September 30, 2015
	U.S.			Int'l			U.S.			Int'l			U.S.			Int'l
	(in millions)
Change in plan assets
Fair value of plan assets at beginning of year	$	456.9		$	973.2		$	459.0		$	925.8		$	139.7		$	532.6
Actual return on plan assets		39.0			9.6			49.6			215.9			(2.8	)		49.9
Employer contributions		12.3			25.8			18.5			20.2			42.1			24.4
Participant contributions		0.1			0.4			0.1			0.5			0.4			0.5
Benefits and expenses paid		(37.9	)		(48.3	)		(37.4	)		(41.9	)		(33.9	)		(41.0	)
Plan settlements		—			—			(32.9	)		(0.7	)		(20.1	)		(2.5	)
Net transfer in/(out)/acquisitions		—			—			—			—			333.6			415.5
Foreign currency translation gain (loss)		—			32.4			—			(146.6	)		—			(53.6	)

Fair value of plan assets at end of year	$	470.4		$	993.1		$	456.9		$	973.2		$	459.0		$	925.8

Reconciliations of the funded status

	Fiscal Year Ended
	September 30, 2017						September 30, 2016						September 30, 2015
	U.S.			Int'l			U.S.			Int'l			U.S.			Int'l
	(in millions)
Reconciliation of funded status:
Funded status at end of year	$	(212.6	)	$	(340.4	)	$	(263.1	)	$	(433.0	)	$	(259.2	)	$	(313.4	)
Contribution made after measurement date		N/A			N/A			N/A			N/A			N/A			N/A

Net amount recognized at end of year	$	(212.6	)	$	(340.4	)	$	(263.1	)	$	(433.0	)	$	(259.2	)	$	(313.4	)

Amounts recognized in the consolidated balance sheets

	Fiscal Year Ended
	September 30, 2017						September 30, 2016						September 30, 2015
	U.S.			Int'l			U.S.			Int'l			U.S.			Int'l
	(in millions)
Amounts recognized in the consolidated balance sheets:
Other non-current assets	$	2.3		$	13.9		$	2.0		$	5.3		$	1.6		$	1.7
Accrued expenses and other current liabilities		(10.1	)		—			(9.3	)		—			(10.6	)		—
Pension benefit obligations		(204.8	)		(354.3	)		(255.8	)		(438.3	)		(250.2	)		(315.1	)

Net amount recognized in the balance sheet	$	(212.6	)	$	(340.4	)	$	(263.1	)	$	(433.0	)	$	(259.2	)	$	(313.4	)

Reconciliation of amounts in the consolidated statements of stockholders' equity

	Fiscal Year Ended
	September 30, 2017						September 30, 2016						September 30, 2015
	U.S.			Int'l			U.S.			Int'l			U.S.			Int'l
	(in millions)
Reconciliation of amounts in consolidated statements of stockholders' equity:
Prior service (cost) credit	$	(0.2	)	$	4.4		$	(0.2	)	$	4.4		$	—		$	5.3
Net loss		(94.6	)		(263.7	)		(129.6	)		(343.3	)		(99.3	)		(183.6	)

Total recognized in accumulated other comprehensive loss	$	(94.8	)	$	(259.3	)	$	(129.8	)	$	(338.9	)	$	(99.3	)	$	(178.3	)

Components of net periodic cost for the Company's pension and post-retirement plans

	Fiscal Year Ended
	September 30, 2017						September 30, 2016						September 30, 2015
	U.S.			Int'l			U.S.			Int'l			U.S.			Int'l
	(in millions)
Components of net periodic (benefit) cost:
Service costs	$	4.3		$	1.3		$	4.3		$	1.0		$	6.8		$	1.1
Interest cost on projected benefit obligation		19.2			28.3			22.0			39.2			28.2			47.1
Expected return on plan assets		(31.0	)		(41.5	)		(30.8	)		(48.0	)		(29.4	)		(49.4	)
Amortization of prior service credits		—			(0.2	)		—			(0.2	)		—			(0.2	)
Amortization of net loss		4.3			13.0			4.0			5.4			4.3			5.9
Curtailment gain recognized		—			—			(6.8	)		—			—			—
Settlement (gain) loss recognized		—			—			(0.9	)		0.1			0.6			0.7

Net periodic (benefit) cost	$	(3.2	)	$	0.9		$	(8.2	)	$	(2.5	)	$	10.5		$	5.2

Amounts included in accumulated other comprehensive loss that are expected to be recognized as components of net periodic benefit cost during the next fiscal year

	U.S.			Int'l
Amortization of prior service credit	$	—		$	0.2
Amortization of net actuarial losses		(4.0	)		(8.2	)

Total	$	(4.0	)	$	(8.0	)

Additional year-end information for pension plans with accumulated benefit obligations in excess of plan assets

	Fiscal Year Ended
	September 30, 2017				September 30, 2016				September 30, 2015
	U.S.		Int'l		U.S.		Int'l		U.S.		Int'l
	(in millions)
Projected benefit obligation	$	658.4	$	1,158.3	$	694.8	$	1,220.3	$	692.5	$	1,226.2
Accumulated benefit obligation		658.4		1,145.7		694.8		1,215.7		686.5		1,222.0
Fair value of plan assets		466.4		804.2		453.2		782.1		455.6		911.2

Schedule of expected future benefit payments

The table below provides the expected future benefit payments, in millions:

Year Ending September 30,	U.S.		Int'l
2018	$	43.0	$	47.4
2019		40.4		47.8
2020		41.5		47.2
2021		41.6		50.3
2022		41.8		52.1
2023 - 2027		205.0		291.9

Total	$	413.3	$	536.7

Schedule of underlying assumptions for the pension plans

	Fiscal Year Ended
	September 30, 2017						September 30, 2016						September 30, 2015
	U.S.			Int'l			U.S.			Int'l			U.S.			Int'l
Weighted-average assumptions to determine benefit obligation:
Discount rate		3.64	%		2.67	%		3.41	%		2.35	%		4.10	%		3.80	%
Salary increase rate		N/A			2.76	%		N/A			2.61	%		3.81	%		2.51	%
Weighted-average assumptions to determine net periodic benefit cost:
Discount rate		3.41	%		2.35	%		4.10	%		3.80	%		3.88	%		3.92	%
Salary increase rate		N/A			2.61	%		N/A			2.65	%		4.50	%		2.65	%
Expected long-term rate of return on plan assets		7.00	%		5.10	%		6.72	%		5.74	%		6.73	%		6.00	%

Summary of the Company's target allocation and pension plan asset allocation, both U.S. and international

							Percentage of Plan Assets as of September 30,
	Target Allocations						2017						2016
	U.S.			Int'l			U.S.			Int'l			U.S.			Int'l
Asset Category:
Equities		43	%		28	%		43	%		27	%		42	%		28	%
Debt		48			35			47			38			49			34
Cash		1			5			1			2			1			7
Property and other		8			32			9			33			8			31

Total		100	%		100	%		100	%		100	%		100	%		100	%

Fair values of the Company's post-retirement benefit plan assets by major asset categories

			Fair Value Measurement as of September 30, 2017
	Total Carrying Value as of September 30, 2017		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in millions)
Cash and cash equivalents	$	22.9	$	13.1	$	9.8	$	—
Equity securities
Global equity securities		0.8		—		0.8		—
Domestic equity securities		7.1		6.2		0.9		—
Investment funds
Diversified funds		212.8		—		212.8		—
Equity funds		467.9		6.4		461.5		—
Fixed income funds		610.6		3.5		607.1		—
Hedge funds		110.1		—		69.9		40.2
Assets held by insurance company		31.3		—		31.3		—

Total	$	1,463.5	$	29.2	$	1,394.1	$	40.2

			Fair Value Measurement as of September 30, 2016
	Total Carrying Value as of September 30, 2016		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in millions)
Cash and cash equivalents	$	70.6	$	14.3	$	56.3	$	—
Equity securities
Global equity securities		49.4		—		49.4		—
Domestic equity securities		57.1		—		57.1		—
Investment funds
Diversified funds		223.1		—		223.1		—
Equity funds		362.0		5.1		356.9		—
Fixed income funds		548.5		3.7		544.8		—
Hedge funds		62.5		—		48.4		14.1
Assets held by insurance company		32.3		—		32.3		—
Other		24.6		—		24.6		—

Total	$	1,430.1	$	23.1	$	1,392.9	$	14.1

Changes in the fair value of the Company's post-retirement plan Level 3 assets

	September 30, 2016 Beginning balance		Actual return on plan assets, relating to assets still held at reporting date			Actual return on plan assets, relating to assets sold during the period		Purchases, sales and settlements		Transfer into / (out of) Level 3		Change due to exchange rate changes		September 30, 2017 Ending balance
	(in millions)
Investment funds
Hedge funds	$	14.1	$	(0.2	)	$	—	$	—	$	26.3	$	—	$	40.2

	September 30, 2015 Beginning balance		Actual return on plan assets, relating to assets still held at reporting date		Actual return on plan assets, relating to assets sold during the period		Purchases, sales and settlements		Transfer into / (out of) Level 3		Change due to exchange rate changes		September 30, 2016 Ending balance
	(in millions)
Investment funds
Hedge funds	$	13.6	$	0.5	$	—	$	—	$	—	$	—	$	14.1

Debt (Tables)

12 Months Ended

Sep. 30, 2017

Debt

Schedule of debt

	September 30, 2017			September 30, 2016
	(in millions)
2014 Credit Agreement	$	908.7		$	1,954.9
2014 Senior Notes		1,600.0			1,600.0
2017 Senior Notes		1,000.0			—
URS Senior Notes		247.7			427.7
Other debt		140.0			142.7

Total debt		3,896.4			4,125.3
Less: Current portion of debt and short-term borrowings		(142.0	)		(366.3	)
Less: Unamortized debt issuance costs		(52.3	)		(56.8	)

Long-term debt	$	3,702.1		$	3,702.2

Schedule of maturities of debt

The following table presents, in millions, scheduled maturities of the Company's debt as of September 30, 2017:

Fiscal Year
2018	$	142.0
2019		154.4
2020		122.6
2021		603.7
2022		256.7
Thereafter		2,617.0

Total	$	3,896.4

Derivative Financial Instruments and Fair Value Measurements (Tables)

12 Months Ended

Sep. 30, 2017

Derivative Financial Instruments and Fair Value Measurements

Notional principle, fixed rates and related expiration dates of outstanding interest rate swap agreements

September 30, 2017
Notional Amount (in millions)		Fixed Rate			Expiration Date
$	300.0		1.63	%	June 2018
	300.0		1.54	%	September 2018

September 30, 2016
Notional Amount (in millions)		Fixed Rate			Expiration Date
$	300.0		1.63	%	June 2018
	300.0		1.54	%	September 2018

Leases (Tables)

12 Months Ended

Sep. 30, 2017

Leases

Schedule of amounts payable under non-cancelable operating lease commitments

The following table presents, in millions, amounts payable under non-cancelable operating lease commitments during the following fiscal years:

Year Ending September 30,
2018	$	259.1
2019		214.8
2020		174.2
2021		139.7
2022		114.9
Thereafter		460.1

Total	$	1,362.8

Share-Based Payments (Tables)

12 Months Ended

Sep. 30, 2017

Share-Based Payments

Schedule of stock option activity

	Number of Options (in millions)			Weighted Average Exercise Price
Balance, September 30, 2014		1.6			27.69
Granted		—			—
Exercised		(0.3	)		24.98
Cancelled		—			—

Balance, September 30, 2015		1.3			28.26


Granted		—			—
Exercised		(0.4	)		23.96
Cancelled		—			—

Balance, September 30, 2016		0.9			30.36


Granted		—			—
Exercised		(0.2	)		26.42
Cancelled		—			—

Balance, September 30, 2017		0.7			31.11


Exercisable as of September 30, 2015		0.7			25.04


Exercisable as of September 30, 2016		0.3			26.99


Exercisable as of September 30, 2017		0.1			27.79

Summary of information concerning outstanding and exercisable options

	Options Outstanding								Options Exercisable
	Number Outstanding as of September 30, 2017 (in millions)		Weighted Average Remaining Contractual Life		Weighted Average Exercise Price		Aggregate Intrinsic Value (in millions)		Number Exercisable as of September 30, 2017 (in millions)		Weighted Average Remaining Contractual Life		Weighted Average Exercise Price
Range of Exercise Prices
$27.54 - $28.44		0.1		0.27	$	27.79	$	0.9		0.1		0.27	$	27.79
$31.62		0.6		6.43		31.62		3.3		—		—		—

		0.7		5.61		31.11	$	4.2		0.1		0.27		27.79

Income Taxes (Tables)

12 Months Ended

Sep. 30, 2017

Income Taxes

Schedule of income tax (benefit) expense

	Fiscal Year Ended
	September 30, 2017			September 30, 2016			September 30, 2015
	(in millions)
Current:
Federal	$	10.3		$	33.7		$	(67.1	)
State		17.9			12.4			2.6
Foreign		29.3			26.1			37.2

Total current income tax expense (benefit)		57.5			72.2			(27.3	)

Deferred:
Federal		(8.3	)		(63.4	)		(44.2	)
State		10.4			(5.4	)		1.2
Foreign		(51.9	)		(41.3	)		(10.0	)

Total deferred income tax (benefit) expense		(49.8	)		(110.1	)		(53.0	)

Total income tax expense (benefit)	$	7.7		$	(37.9	)	$	(80.3	)

Major elements contributing to the difference between the U.S. federal statutory rate of 35.0% and the effective tax rate

	Fiscal Year Ended
	September 30, 2017						September 30, 2016						September 30, 2015
	Amount			%			Amount			%			Amount			%
	(in millions)
Tax at federal statutory rate	$	150.3			35.0	%	$	43.9			35.0	%	$	(53.0	)		35.0	%
State income tax, net of federal benefit		24.3			5.7			5.6			4.5			(2.3	)		1.5
Income tax credits and incentives		(56.8	)		(13.2	)		(24.6	)		(19.6	)		(21.2	)		14.0
Valuation allowance		(51.2	)		(11.9	)		(54.8	)		(43.6	)		30.0			(19.8	)
Exclusion of tax on non-controlling interests		(28.2	)		(6.6	)		(24.7	)		(19.7	)		(29.3	)		19.3
Foreign tax rate differential		(19.2	)		(4.5	)		(19.7	)		(15.7	)		(24.8	)		16.4
Tax exempt income		(17.9	)		(4.2	)		(17.6	)		(14.0	)		(13.2	)		8.7
Foreign residual income		(9.2	)		(2.1	)		17.8			14.2			20.1			(13.3	)
Change in uncertain tax positions		9.5			2.2			(5.0	)		(4.0	)		6.6			(4.3	)
Nondeductible costs		5.8			1.4			6.1			4.8			2.8			(1.8	)
Other items, net		0.3			—			0.5			0.3			1.2			(0.9	)
Change in tax rates		—			—			34.6			27.6			—			—
Nondeductible transaction costs		—			—			—			—			2.8			(1.8	)

Total income tax expense	$	7.7			1.8	%	$	(37.9	)		(30.2	)%	$	(80.3	)		53.0	%

Schedule of deferred tax assets (liabilities)

	Fiscal Year Ended
	September 30, 2017			September 30, 2016
	(in millions)
Deferred tax assets:
Compensation and benefit accruals not currently deductible	$	144.2		$	150.5
Net operating loss carryforwards		338.2			378.0
Self insurance reserves		23.8			24.7
Research and experimentation and other tax credits		167.5			125.3
Pension liability		142.1			180.9
Accrued liabilities		160.7			221.0
Other		25.0			4.3

Total deferred tax assets		1,001.5			1,084.7

Deferred tax liabilities:
Unearned revenue		(190.8	)		(212.6	)
Depreciation and amortization		(158.6	)		(113.0	)
Acquired intangible assets		(121.7	)		(155.5	)
Investment in subsidiaries		(241.2	)		(261.4	)

Total deferred tax liabilities		(712.3	)		(742.5	)

Valuation allowance		(138.4	)		(183.8	)

Net deferred tax assets	$	150.8		$	158.4

Reconciliation of the beginning and ending amount of gross unrecognized tax benefits

	Fiscal Year Ended
	September 30, 2017			September 30, 2016
	(in millions)
Balance at the beginning of the year	$	87.9		$	95.2
Gross increase due to acquisitions		—			—
Gross increase in current period's tax positions		10.8			7.6
Gross increase in prior years' tax positions		5.3			5.2
Gross decrease in prior years' tax positions		—			(16.6	)
Decrease due to settlement with tax authorities		(1.0	)		(3.2	)
Decrease due to lapse of statute of limitations		(1.1	)		(1.8	)
Gross change due to foreign exchange fluctuations		0.2			1.5

Balance at the end of the year	$	102.1		$	87.9

Earnings Per Share (Tables)

12 Months Ended

Sep. 30, 2017

Earnings Per Share

Reconciliation of the denominators for basic and diluted EPS

	Fiscal Year Ended
	September 30, 2017		September 30, 2016		September 30, 2015
	(in millions)
Denominator for basic earnings per share		155.7		154.8		149.6
Potential common shares		3.4		1.3		—

Denominator for diluted earnings per share		159.1		156.1		149.6

Other Financial Information (Tables)

12 Months Ended

Sep. 30, 2017

Other Financial Information

Schedule of accrued expenses and other current liabilities

	Fiscal Year Ended
	September 30, 2017		September 30, 2016
	(in millions)
Accrued salaries and benefits	$	1,018.5	$	964.9
Accrued contract costs		911.9		1,009.8
Other accrued expenses		315.1		410.1

	$	2,245.5	$	2,384.8

Reclassifications out of Accumulated Other Comprehensive Loss (Tables)

12 Months Ended

Sep. 30, 2017

Reclassifications out of Accumulated Other Comprehensive Loss

Schedule of accumulated balances and reporting period activities related to reclassifications out of accumulated other comprehensive loss

	Pension Related Adjustments			Foreign Currency Translation Adjustments			Loss on Derivative Instruments			Accumulated Other Comprehensive Loss
Balances at September 30, 2014	$	(217.0	)	$	(137.8	)	$	(1.8	)	$	(356.6	)
Other comprehensive income (loss) before reclassification		5.8			(282.3	)		(13.3	)		(289.8	)
Amounts reclassified from accumulated other comprehensive loss		7.2			—			4.1			11.3

Balances at September 30, 2015	$	(204.0	)	$	(420.1	)	$	(11.0	)	$	(635.1	)

	Pension Related Adjustments			Foreign Currency Translation Adjustments			Loss on Derivative Instruments			Accumulated Other Comprehensive Loss
Balances at September 30, 2015	$	(204.0	)	$	(420.1	)	$	(11.0	)	$	(635.1	)
Other comprehensive income (loss) before reclassification		(171.5	)		(63.6	)		1.2			(233.9	)
Amounts reclassified from accumulated other comprehensive loss		6.6			—			4.8			11.4

Balances at September 30, 2016	$	(368.9	)	$	(483.7	)	$	(5.0	)	$	(857.6	)

	Pension Related Adjustments			Foreign Currency Translation Adjustments			Loss on Derivative Instruments			Accumulated Other Comprehensive Loss
Balances at September 30, 2016	$	(368.9	)	$	(483.7	)	$	(5.0	)	$	(857.6	)
Other comprehensive income (loss) before reclassification		73.8			65.3			2.3			141.4
Amounts reclassified from accumulated other comprehensive loss		13.2			—			2.3			15.5

Balances at September 30, 2017	$	(281.9	)	$	(418.4	)	$	(0.4	)	$	(700.7	)

Reportable Segments and Geographic Information (Tables)

12 Months Ended

Sep. 30, 2017

Reportable Segments and Geographic Information

Summarized financial information concerning the Company's reportable segments

Reportable Segments:	Design and Consulting Services			Construction Services			Management Services			AECOM Capital			Corporate			Total
	(in millions)
Fiscal Year Ended September 30, 2017:
Revenue	$	7,566.8		$	7,295.6		$	3,341.0		$	—		$	—		$	18,203.4
Gross profit		394.8			92.9			196.0			—			—			683.7
Equity in earnings of joint ventures		16.4			22.4			45.1			57.7			—			141.6
General and administrative expenses		—			—			—			(8.7	)		(124.7	)		(133.4	)
Acquisition and integration expenses		—			—			—			—			(38.7	)		(38.7	)
Gain on disposal activities		0.6			—			—			—			—			0.6
Operating income		411.8			115.3			241.1			49.0			(163.4	)		653.8
Segment assets		6,992.6			4,114.5			2,704.6			199.1			386.2			14,397.0
Gross profit as a % of revenue		5.2	%		1.3	%		5.9	%								3.8	%
Fiscal Year Ended September 30, 2016:
Revenue	$	7,655.8		$	6,371.1		$	3,383.9		$	—		$	—		$	17,410.8
Gross profit		382.5			25.4			234.9			—			—			642.8
Equity in earnings of joint ventures		8.9			18.2			76.9			—			—			104.0
General and administrative expenses		—			—			—			(6.0	)		(109.1	)		(115.1	)
Acquisition and integration expenses		—			—			—			—			(213.6	)		(213.6	)
Loss on disposal activities		—			(42.6	)		—			—			—			(42.6	)
Operating income		391.4			1.0			311.8			(6.0	)		(322.7	)		375.5
Segment assets		6,655.7			3,556.2			2,692.7			179.1			586.2			13,669.9
Gross profit as a % of revenue		5.0	%		0.4	%		6.9	%								3.7	%
Fiscal Year Ended September 30, 2015:
Revenue	$	7,962.9		$	6,539.3		$	3,487.7		$	—		$	—		$	17,989.9
Gross profit		299.3			35.9			200.0			—			—			535.2
Equity in earnings of joint ventures		6.6			23.0			76.6			—			—			106.2
General and administrative expenses		—			—			—			(4.3	)		(109.7	)		(114.0	)
Acquisition and integration expenses		—			—			—			—			(398.4	)		(398.4	)
Operating income		305.9			58.9			276.6			(4.3	)		(508.1	)		129.0
Segment assets		7,118.2			3,382.4			2,903.9			111.7			498.1			14,014.3
Gross profit as a % of revenue		3.8	%		0.5	%		5.7	%								3.0	%

Schedule of geographic information

	Fiscal Year Ended
	September 30, 2017				September 30, 2016				September 30, 2015
	Revenue		Long-Lived Assets		Revenue		Long-Lived Assets		Revenue		Long-Lived Assets
	(in millions)
United States	$	13,042.6		4,779.0	$	12,567.0		4,763.9	$	12,599.6		4,852.5
Asia Pacific		1,352.7		382.9		1,278.3		394.0		1,385.3		426.4
Canada		1,159.9		600.4		866.5		615.7		1,308.3		641.0
Europe		1,869.9		1,362.8		1,904.2		1,368.4		1,796.9		1,496.2
Other foreign countries		778.3		418.3		794.8		412.5		899.8		352.1

Total	$	18,203.4		7,543.4	$	17,410.8		7,554.5	$	17,989.9		7,768.2

Quarterly Financial Information-Unaudited (Tables)

12 Months Ended

Sep. 30, 2017

Quarterly Financial Information-Unaudited

Schedule of unaudited quarterly data

Fiscal Year 2017:	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
	(in millions, except per share data)
Revenue	$	4,358.3		$	4,427.2		$	4,561.5		$	4,856.4
Cost of revenue		4,188.3			4,258.8			4,386.3			4,686.3

Gross profit		170.0			168.4			175.2			170.1
Equity in earnings of joint ventures		21.4			21.8			66.5			31.9
General and administrative expenses		(32.6	)		(29.9	)		(34.0	)		(36.9	)
Acquisition and integration expenses		(15.4	)		(20.0	)		—			(3.3	)
Gain on disposal activities		—			0.6			—			—

Income from operations		143.4			140.9			207.7			161.8
Other income		0.8			1.3			2.1			2.5
Interest expense		(53.6	)		(61.8	)		(61.6	)		(54.3	)

Income before income tax expense		90.6			80.4			148.2			110.0
Income tax expense (benefit)		24.8			(35.4	)		12.1			6.2

Net income		65.8			115.8			136.1			103.8
Noncontrolling interest in income of consolidated subsidiaries, net of tax		(18.6	)		(13.4	)		(34.8	)		(15.3	)

Net income attributable to AECOM	$	47.2		$	102.4		$	101.3		$	88.5


Net income attributable to AECOM per share:
Basic	$	0.31		$	0.66		$	0.65		$	0.56
Diluted	$	0.30		$	0.65		$	0.64		$	0.55
Weighted average common shares outstanding:
Basic		154.3			155.4			155.8			157.5
Diluted		158.0			158.7			158.8			161.1

Fiscal Year 2016:	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
	(in millions, except per share data)
Revenue	$	4,297.7		$	4,381.2		$	4,408.8		$	4,323.1
Cost of revenue		4,156.8			4,197.8			4,237.5			4,175.9

Gross profit		140.9			183.4			171.3			147.2
Equity in earnings of joint ventures		25.2			39.1			18.5			21.2
General and administrative expenses		(28.7	)		(29.5	)		(28.7	)		(28.2	)
Acquisition and integration expenses		(41.0	)		(50.7	)		(50.7	)		(71.2	)
Loss on disposal activities		(41.0	)		(1.6	)		—			—

Income from operations		55.4			140.7			110.4			69.0
Other income		3.0			0.8			1.5			2.9
Interest expense		(59.5	)		(62.7	)		(62.6	)		(73.3	)

(Loss) / income before income tax expense		(1.1	)		78.8			49.3			(1.4	)
Income tax (benefit) expense		(0.7	)		12.2			(35.1	)		(14.3	)

Net (loss) / income		(0.4	)		66.6			84.4			12.9
Noncontrolling interest in income of consolidated subsidiaries, net of tax		(20.0	)		(24.7	)		(17.0	)		(5.7	)

Net (loss) / income attributable to AECOM	$	(20.4	)	$	41.9		$	67.4		$	7.2


Net (loss) / income attributable to AECOM per share:
Basic	$	(0.13	)	$	0.27		$	0.44		$	0.05
Diluted	$	(0.13	)	$	0.27		$	0.43		$	0.05
Weighted average common shares outstanding:
Basic		153.6			154.3			154.9			156.3
Diluted		153.6			155.4			156.2			157.9

Condensed Consolidating Financial Information (Tables)

12 Months Ended

Sep. 30, 2017

Condensed Consolidating Financial Information

Schedule of Condensed Consolidating Balance Sheets

Condensed Consolidating Balance Sheets
(in millions)
September 30, 2017

	Parent		Guarantor Subsidiaries		Non- Guarantor Subsidiaries		Eliminations			Total
ASSETS
CURRENT ASSETS:
Total cash and cash equivalents	$	32.6	$	251.6	$	518.2	$	—		$	802.4
Accounts receivable—net		—		2,159.2		2,968.5		—			5,127.7
Intercompany receivable		723.6		90.9		181.4		(995.9	)		—
Prepaid expenses and other current assets		67.5		338.4		290.8		—			696.7
Income taxes receivable		4.3		—		51.1		—			55.4

TOTAL CURRENT ASSETS		828.0		2,840.1		4,010.0		(995.9	)		6,682.2
PROPERTY AND EQUIPMENT—NET		160.2		207.1		254.1		—			621.4
DEFERRED TAX ASSETS—NET		239.7		55.2		171.0		(294.6	)		171.3
INVESTMENTS IN CONSOLIDATED JOINT VENTURES		6,606.2		2,865.0		—		(9,471.2	)		—
INVESTMENTS IN UNCONSOLIDATED JOINT VENTURES		7.2		50.3		306.7		—			364.2
GOODWILL		—		3,318.6		2,674.3		—			5,992.9
INTANGIBLE ASSETS—NET		—		271.6		143.5		—			415.1
OTHER NON-CURRENT ASSETS		8.7		17.6		123.6		—			149.9

TOTAL ASSETS	$	7,850.0	$	9,625.5	$	7,683.2	$	(10,761.7	)	$	14,397.0


LIABILITIES AND STOCKHOLDERS' EQUITY
CURRENT LIABILITIES:
Short-term debt	$	1.1	$	—	$	0.1	$	—		$	1.2
Accounts payable		33.8		1,023.7		1,192.4		—			2,249.9
Accrued expenses and other current liabilities		92.2		1,112.9		1,040.4		—			2,245.5
Accrued taxes payable		—		—		38.2		—			38.2
Intercompany payable		149.2		787.5		161.4		(1,098.1	)		—
Billings in excess of costs on uncompleted contracts		3.4		313.1		586.3		—			902.8
Current portion of long-term debt		110.9		14.9		15.0		—			140.8

TOTAL CURRENT LIABILITIES		390.6		3,252.1		3,033.8		(1,098.1	)		5,578.4
OTHER LONG-TERM LIABILITIES		102.3		285.7		493.3		—			881.3
DEFERRED TAX LIABILITY—NET		—		—		315.1		(294.6	)		20.5
NOTE PAYABLE INTERCOMPANY—NON CURRENT		0.1		—		467.2		(467.3	)		—
LONG-TERM DEBT		3,366.9		281.6		53.6		—			3,702.1

TOTAL LIABILITIES		3,859.9		3,819.4		4,363.0		(1,860.0	)		10,182.3
TOTAL AECOM STOCKHOLDERS' EQUITY		3,990.1		5,806.1		3,101.6		(8,901.7	)		3,996.1
Noncontrolling interests		—		—		218.6		—			218.6

TOTAL STOCKHOLDERS' EQUITY		3,990.1		5,806.1		3,320.2		(8,901.7	)		4,214.7

TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$	7,850.0	$	9,625.5	$	7,683.2	$	(10,761.7	)	$	14,397.0

Condensed Consolidating Balance Sheets
(in millions)
September 30, 2016

	Parent		Guarantor Subsidiaries		Non- Guarantor Subsidiaries		Eliminations			Total
ASSETS
CURRENT ASSETS:
Total cash and cash equivalents	$	1.8	$	183.7	$	506.6	$	—		$	692.1
Accounts receivable—net		—		2,034.0		2,497.5		—			4,531.5
Intercompany receivable		760.7		151.7		152.0		(1,064.4	)		—
Prepaid expenses and other current assets		98.7		336.2		295.2		—			730.1
Income taxes receivable		28.7		—		18.4		—			47.1

TOTAL CURRENT ASSETS		889.9		2,705.6		3,469.7		(1,064.4	)		6,000.8
PROPERTY AND EQUIPMENT—NET		169.3		236.5		239.2		—			645.0
DEFERRED TAX ASSETS—NET		265.2		—		129.8		(223.5	)		171.5
INVESTMENTS IN CONSOLIDATED SUBSIDIARIES		6,031.7		2,681.5		—		(8,713.2	)		—
INVESTMENTS IN UNCONSOLIDATED JOINT VENTURES		0.7		48.6		281.2		—			330.5
GOODWILL		—		3,286.6		2,537.2		—			5,823.8
INTANGIBLE ASSETS—NET		—		334.0		145.4		—			479.4
OTHER NON-CURRENT ASSETS		8.2		71.5		139.2		—			218.9

TOTAL ASSETS	$	7,365.0	$	9,364.3	$	6,941.7	$	(10,001.1	)	$	13,669.9


LIABILITIES AND STOCKHOLDERS' EQUITY
CURRENT LIABILITIES:
Short-term debt	$	3.1	$	7.3	$	15.9	$	—		$	26.3
Accounts payable		45.8		907.0		958.1		—			1,910.9
Accrued expenses and other current liabilities		201.2		1,137.1		1,046.5		—			2,384.8
Accrued taxes payable		—		—		10.8		—			10.8
Intercompany payable		114.1		857.9		208.8		(1,180.8	)		—
Billings in excess of costs on uncompleted contracts		—		237.5		394.4		—			631.9
Current portion of long-term debt		108.2		222.1		9.7		—			340.0

TOTAL CURRENT LIABILITIES		472.4		3,368.9		2,644.2		(1,180.8	)		5,304.7
OTHER LONG-TERM LIABILITIES		115.7		349.3		632.4		—			1,097.4
DEFERRED TAX LIABILITY—NET		—		236.6		—		(223.5	)		13.1
NOTE PAYABLE INTERCOMPANY—NON CURRENT		—		—		563.5		(563.5	)		—
LONG-TERM DEBT		3,411.2		273.4		17.6		—			3,702.2

TOTAL LIABILITIES		3,999.3		4,228.2		3,857.7		(1,967.8	)		10,117.4
TOTAL AECOM STOCKHOLDERS' EQUITY		3,365.7		5,136.1		2,898.4		(8,033.3	)		3,366.9
Noncontrolling interests		—		—		185.6		—			185.6

TOTAL STOCKHOLDERS' EQUITY		3,365.7		5,136.1		3,084.0		(8,033.3	)		3,552.5

TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$	7,365.0	$	9,364.3	$	6,941.7	$	(10,001.1	)	$	13,669.9

Schedule of Condensed Consolidating Statements of Operations

Condensed Consolidating Statements of Operations
(in millions)

	For the Fiscal Year Ended September 30, 2017
	Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Total
Revenue	$	—		$	9,367.1		$	8,905.0		$	(68.7	)	$	18,203.4
Cost of revenue		—			9,000.3			8,588.1			(68.7	)		17,519.7

Gross profit		—			366.8			316.9			—			683.7
Equity in earnings from subsidiaries		439.3			217.2			—			(656.5	)		—
Equity in earnings of joint ventures		—			25.4			116.2			—			141.6
General and administrative expenses		(124.7	)		—			(8.7	)		—			(133.4	)
Acquisition and integration expenses		(38.7	)		—			—			—			(38.7	)
Gain on disposal activities		—			—			0.6			—			0.6

Income from operations		275.9			609.4			425.0			(656.5	)		653.8
Other income		2.2			31.7			9.3			(36.5	)		6.7
Interest expense		(203.7	)		(26.5	)		(37.6	)		36.5			(231.3	)

Income before income tax (benefit) expense		74.4			614.6			396.7			(656.5	)		429.2
Income tax (benefit) expense		(264.9	)		175.8			65.1			31.7			7.7

Net income		339.3			438.8			331.6			(688.2	)		421.5
Noncontrolling interests in income of consolidated subsidiaries, net of tax		—			—			(82.1	)		—			(82.1	)

Net income attributable to AECOM	$	339.3		$	438.8		$	249.5		$	(688.2	)	$	339.4

	For the Fiscal Year Ended September 30, 2016
	Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Total
Revenue	$	—		$	9,227.5		$	8,265.3		$	(82.0	)	$	17,410.8
Cost of revenue		—			8,909.4			7,940.6			(82.0	)		16,768.0

Gross profit		—			318.1			324.7			—			642.8
Equity in earnings from subsidiaries		437.4			243.6			—			(681.0	)		—
Equity in earnings of joint ventures		—			27.3			76.7			—			104.0
General and administrative expenses		(114.0	)		(1.1	)		—			—			(115.1	)
Acquisition and integration expenses		(213.6	)		—			—			—			(213.6	)
Loss on disposal activities		—			—			(42.6	)		—			(42.6	)

Income from operations		109.8			587.9			358.8			(681.0	)		375.5
Other income		0.8			34.7			12.7			(40.0	)		8.2
Interest expense		(231.7	)		(23.6	)		(42.8	)		40.0			(258.1	)

Income (loss) before income tax expense		(121.1	)		599.0			328.7			(681.0	)		125.6
Income tax (benefit) expense		(217.3	)		114.3			27.8			37.3			(37.9	)

Net income		96.2			484.7			300.9			(718.3	)		163.5
Noncontrolling interests in income of consolidated subsidiaries, net of tax		—			—			(67.4	)		—			(67.4	)

Net income attributable to AECOM	$	96.2		$	484.7		$	233.5		$	(718.3	)	$	96.1

	For the Fiscal Year Ended September 30, 2015
	Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Total
Revenue	$	—		$	8,749.5		$	9,463.6		$	(223.2	)	$	17,989.9
Cost of revenue		—			8,486.4			9,191.5			(223.2	)		17,454.7

Gross profit		—			263.1			272.1			—			535.2
Equity in earnings from subsidiaries		321.3			198.9			—			(520.2	)		—
Equity in earnings of joint ventures		—			20.0			86.2			—			106.2
General and administrative expenses		(112.2	)		(1.8	)		—			—			(114.0	)
Acquisition and integration expenses		(346.9	)		(51.5	)		—			—			(398.4	)

(Loss) income from operations		(137.8	)		428.7			358.3			(520.2	)		129.0
Other income		5.1			34.9			14.7			(35.6	)		19.1
Interest expense		(275.4	)		(20.4	)		(39.4	)		35.6			(299.6	)

(Loss) income before income tax expense		(408.1	)		443.2			333.6			(520.2	)		(151.5	)
Income tax (benefit) expense		(253.3	)		66.7			61.0			45.3			(80.3	)

Net (loss) income		(154.8	)		376.5			272.6			(565.5	)		(71.2	)
Noncontrolling interests in income of consolidated subsidiaries, net of tax		—			—			(83.6	)		—			(83.6	)

Net (loss) income attributable to AECOM	$	(154.8	)	$	376.5		$	189.0		$	(565.5	)	$	(154.8	)

Schedule of Consolidating Statements of Comprehensive Income

Consolidating Statements of Comprehensive Income (Loss)
(in millions)

	For the Fiscal Year Ended September 30, 2017
	Parent		Guarantor Subsidiaries		Non-Guarantor Subsidiaries			Eliminations			Total
Net income	$	339.3	$	438.8	$	331.6		$	(688.2	)	$	421.5
Other comprehensive income (loss), net of tax:
Net unrealized gain (loss) on derivatives, net of tax		4.9		—		(0.3	)		—			4.6
Foreign currency translation adjustments		—		—		65.4			—			65.4
Pension adjustments, net of tax		7.1		13.8		66.1			—			87.0

Other comprehensive income, net of tax		12.0		13.8		131.2			—			157.0

Comprehensive income, net of tax		351.3		452.6		462.8			(688.2	)		578.5
Noncontrolling interests in comprehensive income of consolidated subsidiaries, net of tax		—		—		(82.2	)		—			(82.2	)

Comprehensive income attributable to AECOM, net of tax	$	351.3	$	452.6	$	380.6		$	(688.2	)	$	496.3

	For the Fiscal Year Ended September 30, 2016
	Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Total
Net income	$	96.2		$	484.7		$	300.9		$	(718.3	)	$	163.5
Other comprehensive income (loss), net of tax:
Net unrealized gain on derivatives, net of tax		2.6			—			3.4			—			6.0
Foreign currency translation adjustments		—			—			(65.3	)		—			(65.3	)
Pension adjustments, net of tax		(3.3	)		(14.9	)		(146.7	)		—			(164.9	)

Other comprehensive loss, net of tax		(0.7	)		(14.9	)		(208.6	)		—			(224.2	)

Comprehensive income (loss), net of tax		95.5			469.8			92.3			(718.3	)		(60.7	)
Noncontrolling interests in comprehensive income of consolidated subsidiaries, net of tax		—			—			(65.7	)		—			(65.7	)

Comprehensive income (loss) attributable to AECOM, net of tax	$	95.5		$	469.8		$	26.6		$	(718.3	)	$	(126.4	)

	For the Fiscal Year Ended September 30, 2015
	Parent			Guarantor Subsidiaries		Non-Guarantor Subsidiaries			Eliminations			Total
Net (loss) income	$	(154.8	)	$	376.5	$	272.6		$	(565.5	)	$	(71.2	)
Other comprehensive income (loss), net of tax:
Net unrealized loss on derivatives, net of tax		(6.1	)		—		(3.1	)		—			(9.2	)
Foreign currency translation adjustments		—			—		(285.6	)		—			(285.6	)
Pension adjustments, net of tax		1.8			6.4		4.8			—			13.0

Other comprehensive (loss) income, net of tax		(4.3	)		6.4		(283.9	)		—			(281.8	)

Comprehensive (loss) income, net of tax		(159.1	)		382.9		(11.3	)		(565.5	)		(353.0	)
Noncontrolling interests in comprehensive income of consolidated subsidiaries, net of tax		—			—		(80.3	)		—			(80.3	)

Comprehensive (loss) income attributable to AECOM, net of tax	$	(159.1	)	$	382.9	$	(91.6	)	$	(565.5	)	$	(433.3	)

Schedule on Condensed Consolidating Statements of Cash Flows

Condensed Consolidating Statements of Cash Flows
(in millions)

	For the Fiscal Year Ended September 30, 2017
	Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Total
CASH FLOWS FROM OPERATING ACTIVITIES	$	(5.9	)	$	691.2		$	11.4		$	—		$	696.7
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments for business acquisitions, net of cash acquired		—			—			(103.1	)		—			(103.1	)
Proceeds from disposal of business, net of cash disposed		—			—			2.2			—			2.2
Net investment in unconsolidated joint ventures		—			(2.6	)		(21.7	)		—			(24.3	)
Net purchases of investments		—			—			0.9			—			0.9
Payments for capital expenditures, net of disposals		(21.7	)		(29.3	)		(27.4	)		—			(78.4	)
Net investment in intercompany notes		(4.6	)		102.8			12.2			(110.4	)		—
Other intercompany investing activities		139.0			(221.0	)		—			82.0			—

Net cash provided by (used in) investing activities		112.7			(150.1	)		(136.9	)		(28.4	)		(202.7	)

CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from borrowings under credit agreements		5,903.5			13.1			36.6			—			5,953.2
Repayments of borrowings under credit agreements		(6,956.3	)		(51.1	)		(64.2	)		—			(7,071.6	)
Issuance of unsecured senior notes		1,000.0			—			—			—			1,000.0
Redemption of unsecured senior notes		—			(179.2	)		—			—			(179.2	)
Cash paid for debt and equity issuance costs		(13.0	)		—			—			—			(13.0	)
Proceeds from issuance of common stock		30.1			—			—			—			30.1
Proceeds from exercise of stock options		4.9			—			—			—			4.9
Payments to repurchase common stock		(25.1	)		—			—			—			(25.1	)
Net distributions to noncontrolling interests		—			—			(59.0	)		—			(59.0	)
Other financing activities		(24.1	)		(38.3	)		35.6			—			(26.8	)
Net borrowings (repayments) on intercompany notes		4.0			(16.3	)		(98.1	)		110.4			—
Other intercompany financing activities		—			(201.4	)		283.4			(82.0	)		—

Net cash (used in) provided by financing activities		(76.0	)		(473.2	)		134.3			28.4			(386.5	)

EFFECT OF EXCHANGE RATE CHANGES ON CASH		—			—			2.8			—			2.8
NET INCREASE IN CASH AND CASH EQUIVALENTS		30.8			67.9			11.6			—			110.3
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR		1.8			183.7			506.6			—			692.1

CASH AND CASH EQUIVALENTS AT END OF YEAR	$	32.6		$	251.6		$	518.2		$	—		$	802.4

	For the Fiscal Year Ended September 30, 2016
	Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Total
CASH FLOWS FROM OPERATING ACTIVITIES	$	(273.6	)	$	623.7		$	464.1		$	—		$	814.2
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments for business acquisitions, net of cash acquired		—			(1.0	)		(4.5	)		—			(5.5	)
Proceeds from disposal of businesses and property		—			—			39.7			—			39.7
Net investment in unconsolidated joint ventures		—			(3.9	)		(67.6	)		—			(71.5	)
Net sales of investments		—			—			11.5			—			11.5
Payments for capital expenditures, net of disposals		(82.0	)		(58.7	)		3.9			—			(136.8	)
Net receipts from (investment in) intercompany notes		5.3			176.1			(13.5	)		(167.9	)		—
Other intercompany investing activities		791.2			140.3			—			(931.5	)		—

Net cash provided by (used in) investing activities		714.5			252.8			(30.5	)		(1,099.4	)		(162.6	)

CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from borrowings under credit agreements		4,673.0			17.6			15.6			—			4,706.2
Repayments of borrowings under credit agreements		(5,124.1	)		(22.8	)		(53.1	)		—			(5,200.0	)
Cash paid for debt and equity issuance costs		(10.4	)		—			—			—			(10.4	)
Proceeds from issuance of common stock		28.2			—			—			—			28.2
Proceeds from exercise of stock options		9.9			—			—			—			9.9
Payments to repurchase common stock		(25.9	)		—			—			—			(25.9	)
Excess tax benefit from share-based payment		—			—			—			—			—
Net distributions to noncontrolling interests		—			—			(103.2	)		—			(103.2	)
Other financing activities		7.9			(4.5	)		(46.3	)		—			(42.9	)
Net borrowings (repayments) on intercompany notes		1.0			12.5			(181.4	)		167.9			—
Other intercompany financing activities		—			(858.1	)		(73.4	)		931.5			—

Net cash used in financing activities		(440.4	)		(855.3	)		(441.8	)		1,099.4			(638.1	)

EFFECT OF EXCHANGE RATE CHANGES ON CASH		—			—			(5.3	)		—			(5.3	)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS		0.5			21.2			(13.5	)		—			8.2
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR		1.3			162.5			520.1			—			683.9

CASH AND CASH EQUIVALENTS AT END OF YEAR	$	1.8		$	183.7		$	506.6		$	—		$	692.1

	For the Fiscal Year Ended September 30, 2015
	Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Total
CASH FLOWS FROM OPERATING ACTIVITIES	$	(551.2	)	$	816.9		$	498.7		$	—		$	764.4
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments for business acquisitions, net of cash acquired		(3,564.2	)		109.2			161.7			—			(3,293.3	)
Proceeds from disposal of businesses and property		9.5			5.6			—			—			15.1
Net investment in unconsolidated joint ventures		—			(4.0	)		(28.7	)		—			(32.7	)
Sales (purchases) of investments		37.3			—			(2.7	)		—			34.6
Payments for capital expenditures, net of disposals		(51.9	)		(15.8	)		(1.7	)		—			(69.4	)
Receipts from intercompany notes receivable		95.6			128.6			—			(224.2	)		—
Other intercompany investing activities		1,085.8			160.9			—			(1,246.7	)		—

Net cash (used in) provided by investing activities		(2,387.9	)		384.5			128.6			(1,470.9	)		(3,345.7	)

CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from borrowings under credit agreements		6,464.6			29.9			87.2			—			6,581.7
Repayments of borrowings under credit agreements		(5,031.9	)		(31.2	)		(95.2	)		—			(5,158.3	)
Issuance of unsecured senior notes		1,600.0			—			—			—			1,600.0
Prepayment penalty on Unsecured Senior Notes		(55.6	)		—			—			—			(55.6	)
Cash paid for debt and equity issuance costs		(89.6	)		—			—			—			(89.6	)
Proceeds from issuance of common stock		25.6			—			—			—			25.6
Proceeds from exercise of stock options		11.1			—			—			—			11.1
Payments to repurchase common stock		(23.1	)		—			—			—			(23.1	)
Excess tax benefit from share-based payment		3.6			—			—			—			3.6
Net distributions to noncontrolling interests		—			—			(144.3	)		—			(144.3	)
Other financing activities		2.3			(4.1	)		(29.5	)		—			(31.3	)
Intercompany notes repayments		—			—			(224.2	)		224.2			—
Other intercompany financing activities		—			(1,119.3	)		(127.4	)		1,246.7			—

Net cash provided by (used in) financing activities		2,907.0			(1,124.7	)		(533.4	)		1,470.9			2,719.8

EFFECT OF EXCHANGE RATE CHANGES ON CASH		—			—			(28.8	)		—			(28.8	)
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS		(32.1	)		76.7			65.1			—			109.7
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR		33.4			85.8			455.0			—			574.2

CASH AND CASH EQUIVALENTS AT END OF YEAR	$	1.3		$	162.5		$	520.1		$	—		$	683.9

Significant Accounting Policies - Fiscal Year (Details)	12 Months Ended
Significant Accounting Policies - Fiscal Year (Details)	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Significant Accounting Policies
Length of fiscal year	364 days	364 days	364 days

Significant Accounting Policies - Revenue (Details) $ in Billions	12 Months Ended
	Sep. 30, 2017 USD ($) contract	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)
Revenue Recognition
Subcontractor and other direct costs \| $	$ 9.2	$ 8.4	$ 8.3
Cost-Reimbursable Contracts
Revenue Recognition
Types of contracts (number)	2
Cost Plus Contract
Revenue Recognition
Types of contracts (number)	2
Fixed Price Contract
Revenue Recognition
Types of contracts (number)	2
Revenue \| Cost-Reimbursable Contracts
Revenue Recognition
Concentration (as a percent)	48.00%	53.00%	57.00%
Revenue \| Guaranteed Maximum Price Contract
Revenue Recognition
Concentration (as a percent)	23.00%	15.00%	15.00%
Revenue \| Fixed Price Contract
Revenue Recognition
Concentration (as a percent)	29.00%	32.00%	28.00%
Net receivables \| Contract Claims
Revenue Recognition
Concentration (as a percent)	5.00%	5.00%

Significant Accounting Policies - Property and Equipment (Details)	12 Months Ended
	Sep. 30, 2017
Minimum \| Furniture and Fixtures
Property, Plant and Equipment
Estimated useful live (in years)	3 years
Minimum \| Building and land
Property, Plant and Equipment
Estimated useful live (in years)	10 years
Minimum \| Computer systems and equipment
Property, Plant and Equipment
Estimated useful live (in years)	3 years
Maximum \| Furniture and Fixtures
Property, Plant and Equipment
Estimated useful live (in years)	10 years
Maximum \| Building and land
Property, Plant and Equipment
Estimated useful live (in years)	45 years
Maximum \| Computer systems and equipment
Property, Plant and Equipment
Estimated useful live (in years)	12 years

Significant Accounting Policies - Pension Plans (Details)	12 Months Ended
	Sep. 30, 2017
Significant Accounting Policies
Market-related valuation calculation period (in years)	5 years
Net unrecognized gain (loss) threshold subject to amortization (in percent)	10.00%

New Accounting Pronouncements and Changes in Accounting (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
New Accounting Pronouncements and Changes in Accounting
Other non-current assets	$ 149,846	$ 218,898
Long-term debt	3,702,109	3,702,157
Accounting Standards Update April 2015
New Accounting Pronouncements and Changes in Accounting
Other non-current assets	(52,300)	(56,800)
Long-term debt	$ 52,300	$ 56,800

Business Acquisitions, Goodwill and Intangible Assets - URS Acquisition (Details) - USD ($) $ in Millions		12 Months Ended
	Oct. 17, 2014	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Business acquisition
Amortization of intangible assets		$ 102.7	$ 202.4	$ 391.0
URS
Business acquisition
Ownership acquired (in percent)	100.00%
Total consideration	$ 2,300.0
Consideration paid by issuing stock	1,600.0
Senior notes assumed, net of Company repayments	400.0
Repayment of acquiree term loan as part of consideration	600.0
Repayment of acquiree line of credit as part of consideration	100.0
Estimated Legal settlements and uninsured legal damages	240.0
Amortization of intangible assets		9.4	23.0
Margin fair value liability	$ 149.1
Margin liability recognition period ( in years)	2 years
Carrying value margin fair value liability		8.6
Revenue and related income from operations related to margin fair value liability		6.3	37.2
URS \| Cost of revenue
Business acquisition
Amortization of intangible assets		83.6	183.3
URS \| Non-Controlling Interests
Business acquisition
Amortization of intangible assets		$ (8.5)	$ (13.8)
URS \| Customer relationships, contracts and backlog
Business acquisition
Acquired intangible assets	$ 973.8
URS \| Customer relationships, contracts and backlog \| Minimum
Business acquisition
Useful life (in years)	1 year
URS \| Customer relationships, contracts and backlog \| Maximum
Business acquisition
Useful life (in years)	11 years
URS \| Customer relationships, contracts and backlog \| Weighted Average
Business acquisition
Useful life (in years)	3 years

Business Acquisitions, Goodwill and Intangible Assets - Expenses (Details) - USD ($) $ in Thousands	3 Months Ended							12 Months Ended
	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Business acquisition
Severance and personnel costs								$ 32,000	$ 23,400
Professional service, real estate-related, and other expenses								6,700	190,200
Total	$ 3,300	$ 20,000	$ 15,400	$ 71,200	$ 50,700	$ 50,700	$ 41,000	38,709	213,642	$ 398,440
Severance and personnel costs
Business acquisition
Severance expense								9,800	21,800
Severance expense paid								$ 6,900	$ 19,300

Business Acquisitions, Goodwill and Intangible Assets - Consideration (Details) $ in Thousands		3 Months Ended								12 Months Ended
	Oct. 17, 2014 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2017 USD ($) item	Sep. 30, 2016 USD ($) item	Sep. 30, 2015 USD ($) item
Business acquisition
Number of business acquisitions (in entities) \| item										2	1	1
Consideration paid
Equity issued		$ 36,611								$ 36,611		$ 1,554,912
Disposal activities
Loss on disposal activities				$ 600				$ (1,600)	$ (41,000)	572	$ (42,589)
Net income (loss)		103,800	$ 136,100	$ 115,800	$ 65,800	$ 12,900	$ 84,400	$ 66,600	$ (400)	421,476	163,472	(71,233)
Acquisitions excluding URS Corporation
Estimated fair values of the assets acquired and liabilities assumed, as of the acquisition dates, from acquisitions
Cash and cash equivalents		28,000								28,000
Other current assets		118,300								118,300
Total identifiable intangible assets		26,300								26,300
Goodwill		127,100								127,100
Other non-current assets		29,500								29,500
Current liabilities		(123,100)								(123,100)
Noncurrent liabilities		(29,300)								(29,300)
Noncontrolling interests		(10,200)								(10,200)
Net assets acquired		166,600								166,600
Consideration paid
Cash Paid										130,000
Equity issued		36,600								36,600
Total consideration										166,600	5,500	$ 27,300
Acquisitions excluding URS Corporation \| Customer relationships, contracts and backlog
Estimated fair values of the assets acquired and liabilities assumed, as of the acquisition dates, from acquisitions
Total identifiable intangible assets		24,500								24,500
Acquisitions excluding URS Corporation \| Trademark / tradename
Estimated fair values of the assets acquired and liabilities assumed, as of the acquisition dates, from acquisitions
Total identifiable intangible assets		1,800								1,800
URS
Consideration paid
Cash Paid	$ 2,300,000
URS \| Non-core
Disposal activities
Loss on disposal activities											(42,600)
Net assets related to the loss on disposal activities		$ 112,800								112,800
Net income (loss)										(9,400)	$ (36,900)
URS \| Customer relationships, contracts and backlog
Estimated fair values of the assets acquired and liabilities assumed, as of the acquisition dates, from acquisitions
Total identifiable intangible assets	$ 973,800
Shimmick Construction Company, Inc
Consideration paid
Cash Paid										$ 165,500

Business Acquisitions, Goodwill and Intangible Assets - Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Changes in the carrying value of goodwill by reporting segment
Goodwill at the beginning of the period	$ 5,823,843	$ 5,820,700
Post-Acquisition Adjustments	127,100	39,400
Disposed	(1,800)	(11,300)
Foreign Exchange Impact	43,800	(25,000)
Goodwill at the end of the period	5,992,881	5,823,843
DCS
Changes in the carrying value of goodwill by reporting segment
Goodwill at the beginning of the period	3,198,200	3,163,300
Post-Acquisition Adjustments	3,800	26,700
Disposed	(1,800)
Foreign Exchange Impact	18,700	8,200
Goodwill at the end of the period	3,218,900	3,198,200
CS
Changes in the carrying value of goodwill by reporting segment
Goodwill at the beginning of the period	915,200	918,500
Post-Acquisition Adjustments	123,300	8,700
Disposed		(11,300)
Foreign Exchange Impact	11,400	(700)
Goodwill at the end of the period	1,049,900	915,200
MS
Changes in the carrying value of goodwill by reporting segment
Goodwill at the beginning of the period	1,710,400	1,738,900
Post-Acquisition Adjustments		4,000
Foreign Exchange Impact	13,700	(32,500)
Goodwill at the end of the period	$ 1,724,100	$ 1,710,400

Business Acquisitions, Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Identifiable intangible assets with finite useful lives
Gross Amount	$ 1,301,900	$ 1,263,500
Accumulated Amortization	(886,800)	(784,100)
Intangible Assets, Net	415,096	479,439
Backlog and customer relationships
Identifiable intangible assets with finite useful lives
Gross Amount	1,283,600	1,247,100
Accumulated Amortization	(870,200)	(767,700)
Intangible Assets, Net	$ 413,400	479,400
Backlog and customer relationships \| Minimum
Identifiable intangible assets with finite useful lives
Amortization Period	1 year
Backlog and customer relationships \| Maximum
Identifiable intangible assets with finite useful lives
Amortization Period	11 years
Trademark / tradename
Identifiable intangible assets with finite useful lives
Gross Amount	$ 18,300	16,400
Accumulated Amortization	(16,600)	$ (16,400)
Intangible Assets, Net	$ 1,700
Trademark / tradename \| Minimum
Identifiable intangible assets with finite useful lives
Amortization Period	3 months 18 days
Trademark / tradename \| Maximum
Identifiable intangible assets with finite useful lives
Amortization Period	2 years

Business Acquisitions, Goodwill and Intangible Assets - Amortization Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Business Acquisitions, Goodwill and Intangible Assets
Amortization expense	$ 102,700	$ 202,400	$ 391,000
Estimated amortization expense for the remainder of fiscal 2017 and for the succeeding years
2018	91,700
2019	84,500
2020	70,500
2021	59,500
2022	46,300
Thereafter	62,600
Intangible Assets, Net	$ 415,096	$ 479,439

Accounts Receivable - Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Billed	$ 2,317,800	$ 2,267,600
Unbilled	2,293,500	1,890,200
Contract retentions	568,600	434,100
Total accounts receivable-gross	5,179,900	4,591,900
Allowance for doubtful accounts	(52,200)	(60,400)
Total accounts receivable-net	$ 5,127,743	$ 4,531,460
Additional disclosures
Unbilled receivables are expected to be billed and collected (in months)	12 months	12 months
Trade receivables sold, outstanding	$ 325,200	$ 356,300
Other than U.S government outstanding receivables
Additional disclosures
Number of Customers	0	0
Outstanding receivables (as a percent)	10.00%	10.00%

Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
Property and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Property and equipment
Property and equipment, gross	$ 1,298,700	$ 1,221,000
Accumulated depreciation and amortization	(677,300)	(576,000)
Property and equipment, net	621,357	644,992
Depreciation expense	157,100	171,700	$ 191,300
Building and land
Property and equipment
Property and equipment, gross	63,600	57,900
Leasehold improvements
Property and equipment
Property and equipment, gross	404,600	381,400
Computer systems and equipment
Property and equipment
Property and equipment, gross	694,600	652,000
Furniture and Fixtures
Property and equipment
Property and equipment, gross	$ 135,900	$ 129,700

Property and Equipment - Useful Lives (Details)	12 Months Ended
Property and Equipment - Useful Lives (Details)	Sep. 30, 2017
Building and land \| Minimum
Property and equipment
Useful Lives	10 years
Building and land \| Maximum
Property and equipment
Useful Lives	45 years
Leasehold improvements \| Minimum
Property and equipment
Useful Lives	1 year
Leasehold improvements \| Maximum
Property and equipment
Useful Lives	20 years
Computer systems and equipment \| Minimum
Property and equipment
Useful Lives	3 years
Computer systems and equipment \| Maximum
Property and equipment
Useful Lives	12 years
Furniture and Fixtures \| Minimum
Property and equipment
Useful Lives	3 years
Furniture and Fixtures \| Maximum
Property and equipment
Useful Lives	10 years

Joint Ventures and Variable Interest Entities - Consolidated (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017 USD ($) item employee	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2017 USD ($) item employee	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)
Financial information
Minimum number of partners required \| item	2								2
Minimum number of employees \| employee	0								0
Current assets	$ 6,682,222				$ 6,000,771				$ 6,682,222	$ 6,000,771
TOTAL ASSETS	14,396,956				13,669,936				14,396,956	13,669,936	$ 14,014,300
Current liabilities	5,578,379				5,304,756				5,578,379	5,304,756
TOTAL LIABILITIES	10,182,270				10,117,447				10,182,270	10,117,447
Total AECOM equity	3,996,126				3,366,921				3,996,126	3,366,921
Noncontrolling interests	218,560				185,568				218,560	185,568
TOTAL STOCKHOLDERS' EQUITY	4,214,686				3,552,489				4,214,686	3,552,489	3,630,943	$ 2,272,480
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	14,396,956				13,669,936				14,396,956	13,669,936
Joint ventures summarized financial information
Revenue	4,856,400	$ 4,561,500	$ 4,427,200	$ 4,358,300	4,323,100	$ 4,408,800	$ 4,381,200	$ 4,297,700	18,203,402	17,410,825	17,989,880
Consolidated Joint Ventures
Financial information
Current assets	832,100				684,100				832,100	684,100
Non-current assets	188,800				230,800				188,800	230,800
TOTAL ASSETS	1,020,900				914,900				1,020,900	914,900
Current liabilities	524,900				407,400				524,900	407,400
Non-current liabilities	12,400				12,400				12,400	12,400
TOTAL LIABILITIES	537,300				419,800				537,300	419,800
Total AECOM equity	274,700				318,000				274,700	318,000
Noncontrolling interests	208,900				177,100				208,900	177,100
TOTAL STOCKHOLDERS' EQUITY	483,600				495,100				483,600	495,100
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 1,020,900				$ 914,900				1,020,900	914,900
Joint ventures summarized financial information
Revenue									$ 1,933,500	$ 1,935,200	$ 2,368,000

Joint Ventures and Variable Interest Entities - Unconsolidated (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Financial information
Current assets	$ 6,682,222				$ 6,000,771				$ 6,682,222	$ 6,000,771
TOTAL ASSETS	14,396,956				13,669,936				14,396,956	13,669,936	$ 14,014,300
Current liabilities	5,578,379				5,304,756				5,578,379	5,304,756
TOTAL LIABILITIES	10,182,270				10,117,447				10,182,270	10,117,447
Total AECOM equity	3,996,126				3,366,921				3,996,126	3,366,921
Noncontrolling interests	218,560				185,568				218,560	185,568
TOTAL STOCKHOLDERS' EQUITY	4,214,686				3,552,489				4,214,686	3,552,489	3,630,943	$ 2,272,480
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	14,396,956				13,669,936				14,396,956	13,669,936
AECOM's investment in joint ventures	364,223				330,485				364,223	330,485
Joint ventures summarized financial information
Revenue	4,856,400	$ 4,561,500	$ 4,427,200	$ 4,358,300	4,323,100	$ 4,408,800	$ 4,381,200	$ 4,297,700	18,203,402	17,410,825	17,989,880
Cost of revenue	4,686,300	4,386,300	4,258,800	4,188,300	4,175,900	4,237,500	4,197,800	4,156,800	17,519,682	16,768,001	17,454,692
Gross profit	170,100	175,200	168,400	170,000	147,200	171,300	183,400	140,900	683,720	642,824	535,188
Net income	103,800	$ 136,100	$ 115,800	$ 65,800	12,900	$ 84,400	$ 66,600	$ (400)	421,476	163,472	$ (71,233)
Unconsolidated Joint Ventures
Financial information
Current assets	1,912,200				1,407,000				1,912,200	1,407,000
Non-current assets	749,800				499,400				749,800	499,400
TOTAL ASSETS	2,662,000				1,906,400				2,662,000	1,906,400
Current liabilities	1,570,200				977,300				1,570,200	977,300
Non-current liabilities	185,100				146,200				185,100	146,200
TOTAL LIABILITIES	1,755,300				1,123,500				1,755,300	1,123,500
TOTAL STOCKHOLDERS' EQUITY	906,700				782,900				906,700	782,900
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	2,662,000				1,906,400				2,662,000	1,906,400
AECOM's investment in joint ventures	$ 364,200				$ 330,500				364,200	330,500
Joint ventures summarized financial information
Revenue									5,561,800	4,871,800
Cost of revenue									5,305,500	4,618,300
Gross profit									256,300	253,500
Net income									$ 244,800	$ 233,900

Joint Ventures and Variable Interest Entities - Equity in Earnings (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Summary of AECOM's equity in earnings of unconsolidated joint ventures:
Equity in earnings of joint ventures	$ 31,900	$ 66,500	$ 21,800	$ 21,400	$ 21,200	$ 18,500	$ 39,100	$ 25,200	$ 141,582	$ 104,032	$ 106,245
Provost Square I LLC
Additional information unconsolidated joint ventures
Gain from sale of interest in joint venture									$ 52,000
Equity interest (in percent)	50.00%								50.00%
Unconsolidated Joint Ventures \| Pass through joint ventures
Summary of AECOM's equity in earnings of unconsolidated joint ventures:
Equity in earnings of joint ventures									$ 36,600	21,900	26,200
Unconsolidated Joint Ventures \| Other Joint Ventures
Summary of AECOM's equity in earnings of unconsolidated joint ventures:
Equity in earnings of joint ventures									$ 105,000	$ 82,100	$ 80,000

Pension Benefit Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
United States Pension Plan of US Entity, Defined Benefit
Change in benefit obligation:
Benefit obligation at beginning of year	$ 720.0	$ 718.2	$ 217.0
Service costs	4.3	4.3	6.8
Participant contributions	0.1	0.1	0.4
Interest cost	19.2	22.0	28.2
Benefits and expenses paid	(37.9)	(37.4)	(33.9)
Actuarial (gain) loss	(22.7)	52.3	(41.0)
Plan settlements		(32.9)	(20.1)
Plan amendments		0.2
Plan curtailments		(6.8)
Net transfer in/(out)/acquisitions			560.8
Benefit obligation at end of year	683.0	720.0	718.2
Foreign Pension Plan, Defined Benefit
Change in benefit obligation:
Benefit obligation at beginning of year	1,406.2	1,239.2	676.6
Service costs	1.3	1.0	1.1
Participant contributions	0.4	0.5	0.5
Interest cost	28.3	39.2	47.1
Benefits and expenses paid	(48.3)	(41.9)	(41.0)
Actuarial (gain) loss	(98.6)	377.1	10.6
Plan settlements		(0.7)	(2.5)
Net transfer in/(out)/acquisitions			618.6
Foreign currency translation loss (gain)	44.2	(208.2)	(71.8)
Benefit obligation at end of year	$ 1,333.5	$ 1,406.2	$ 1,239.2

Pension Benefit Obligations - Asset Changes (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
United States Pension Plan of US Entity, Defined Benefit
Change in plan assets
Fair value of plan assets at beginning of year	$ 456.9	$ 459.0	$ 139.7
Actual return on plan assets	39.0	49.6	(2.8)
Employer contributions	12.3	18.5	42.1
Participant contributions	0.1	0.1	0.4
Benefits and expenses paid	(37.9)	(37.4)	(33.9)
Plan settlements		(32.9)	(20.1)
Net transfer in/(out)/acquisitions			333.6
Fair value of plan assets at end of year	470.4	456.9	459.0
Foreign Pension Plan, Defined Benefit
Change in plan assets
Fair value of plan assets at beginning of year	973.2	925.8	532.6
Actual return on plan assets	9.6	215.9	49.9
Employer contributions	25.8	20.2	24.4
Participant contributions	0.4	0.5	0.5
Benefits and expenses paid	(48.3)	(41.9)	(41.0)
Plan settlements		(0.7)	(2.5)
Net transfer in/(out)/acquisitions			415.5
Foreign currency translation gain (loss)	32.4	(146.6)	(53.6)
Fair value of plan assets at end of year	$ 993.1	$ 973.2	$ 925.8

Pension Benefit Obligations - Funded Status (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
United States Pension Plan of US Entity, Defined Benefit
Reconciliation of funded status:
Funded status at end of year	$ (212.6)	$ (263.1)	$ (259.2)
Net amount recognized at end of year	(212.6)	(263.1)	(259.2)
Foreign Pension Plan, Defined Benefit
Reconciliation of funded status:
Funded status at end of year	(340.4)	(433.0)	(313.4)
Net amount recognized at end of year	$ (340.4)	$ (433.0)	$ (313.4)

Pension Benefit Obligations - Balance Sheet Recognition (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Amounts recognized in the consolidated balance sheets:
Pension benefit obligations	$ (559,068)	$ (694,073)
United States Pension Plan of US Entity, Defined Benefit
Amounts recognized in the consolidated balance sheets:
Other non-current assets	2,300	2,000	$ 1,600
Accrued expenses and other current liabilities	(10,100)	(9,300)	(10,600)
Pension benefit obligations	(204,800)	(255,800)	(250,200)
Net amount recognized in the balance sheet	(212,600)	(263,100)	(259,200)
Foreign Pension Plan, Defined Benefit
Amounts recognized in the consolidated balance sheets:
Other non-current assets	13,900	5,300	1,700
Pension benefit obligations	(354,300)	(438,300)	(315,100)
Net amount recognized in the balance sheet	$ (340,400)	$ (433,000)	$ (313,400)

Pension Benefit Obligations - Equity Recognition (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
United States Pension Plan of US Entity, Defined Benefit
Reconciliation of amounts in consolidated statements of stockholders' equity:
Prior service (cost) credit	$ (0.2)	$ (0.2)
Net loss	(94.6)	(129.6)	$ (99.3)
Total recognized in accumulated other comprehensive loss	(94.8)	(129.8)	(99.3)
Foreign Pension Plan, Defined Benefit
Reconciliation of amounts in consolidated statements of stockholders' equity:
Prior service (cost) credit	4.4	4.4	5.3
Net loss	(263.7)	(343.3)	(183.6)
Total recognized in accumulated other comprehensive loss	$ (259.3)	$ (338.9)	$ (178.3)

Pension Benefit Obligations - Periodic Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Components of net periodic (benefit) cost:
Net of applicable deferred income taxes, included in OCI arising from net prior service cost and net gain/loss	$ (87,061)	$ 164,911	$ (12,953)
Pension Plan, Defined Benefit
Components of net periodic (benefit) cost:
Net of applicable deferred income taxes, included in OCI arising from net prior service cost and net gain/loss	27,600	26,200	6,900
United States Pension Plan of US Entity, Defined Benefit
Components of net periodic (benefit) cost:
Service costs	4,300	4,300	6,800
Interest cost on projected benefit obligation	19,200	22,000	28,200
Expected return on plan assets	(31,000)	(30,800)	(29,400)
Amortization of net loss	4,300	4,000	4,300
Curtailment gain recognized		(6,800)
Settlement (gain) loss recognized		(900)	600
Net periodic (benefit) cost	(3,200)	(8,200)	10,500
Foreign Pension Plan, Defined Benefit
Components of net periodic (benefit) cost:
Service costs	1,300	1,000	1,100
Interest cost on projected benefit obligation	28,300	39,200	47,100
Expected return on plan assets	(41,500)	(48,000)	(49,400)
Amortization of prior service costs	(200)	(200)	(200)
Amortization of net loss	13,000	5,400	5,900
Settlement (gain) loss recognized		100	700
Net periodic (benefit) cost	$ 900	$ (2,500)	$ 5,200

Pension Benefit Obligations - AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
United States Pension Plan of US Entity, Defined Benefit
Amounts included in AOCI that are expected to be recognized as components of net periodic benefit cost during the next fiscal year
Amortization of net actuarial losses	$ (4.0)
Total	(4.0)
Foreign Pension Plan, Defined Benefit
Amounts included in AOCI that are expected to be recognized as components of net periodic benefit cost during the next fiscal year
Amortization of prior service credit	0.2	$ 0.2	$ 0.2
Amortization of net actuarial losses	(8.2)
Total	$ (8.0)

Pension Benefit Obligations - Excess of Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
United States Pension Plan of US Entity, Defined Benefit
Additional year-end information for pension plans with accumulated benefit obligations in excess of plan assets
Projected benefit obligation	$ 658.4	$ 694.8	$ 692.5
Accumulated benefit obligation	658.4	694.8	686.5
Fair values of plan assets	466.4	453.2	455.6
Expected employer contributions in next fiscal year	12.7
Foreign Pension Plan, Defined Benefit
Additional year-end information for pension plans with accumulated benefit obligations in excess of plan assets
Projected benefit obligation	1,158.3	1,220.3	1,226.2
Accumulated benefit obligation	1,145.7	1,215.7	1,222.0
Fair values of plan assets	804.2	$ 782.1	$ 911.2
Expected employer contributions in next fiscal year	$ 26.8

Pension Benefit Obligations - Future payments (Details) $ in Millions	Sep. 30, 2017 USD ($)
United States Pension Plan of US Entity, Defined Benefit
Expected future benefit payments
2018	$ 43.0
2019	40.4
2020	41.5
2021	41.6
2022	41.8
2023-2027	205.0
Total	413.3
Foreign Pension Plan, Defined Benefit
Expected future benefit payments
2018	47.4
2019	47.8
2020	47.2
2021	50.3
2022	52.1
2023-2027	291.9
Total	$ 536.7

Pension Benefit Obligations - Underlying assumptions (Details)	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
United States Pension Plan of US Entity, Defined Benefit
Weighted-average assumptions to determine benefit obligation:
Discount rate (as a percent)	3.64%	3.41%	4.10%
Salary increase rate (as a percent)			3.81%
Weighted-average assumptions to determine net periodic benefit cost:
Discount rate (as a percent)	3.41%	4.10%	3.88%
Salary increase rate (as a percent)			4.50%
Expected long-term rate of return on plan assets (as a percent)	7.00%	6.72%	6.73%
Foreign Pension Plan, Defined Benefit
Weighted-average assumptions to determine benefit obligation:
Discount rate (as a percent)	2.67%	2.35%	3.80%
Salary increase rate (as a percent)	2.76%	2.61%	2.51%
Weighted-average assumptions to determine net periodic benefit cost:
Discount rate (as a percent)	2.35%	3.80%	3.92%
Salary increase rate (as a percent)	2.61%	2.65%	2.65%
Expected long-term rate of return on plan assets (as a percent)	5.10%	5.74%	6.00%

Pension Benefit Obligations - Target Allocation and Plan Assets (Details)	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
United States Pension Plan of US Entity, Defined Benefit
Target Allocations by Asset Category
Target Allocations by Asset Category (as a percent)	100.00%
Percentage of Plan Assets by Category
Plan Assets by Asset Category (as a percent)	100.00%	100.00%
United States Pension Plan of US Entity, Defined Benefit \| Equity Securities
Target Allocations by Asset Category
Target Allocations by Asset Category (as a percent)	43.00%
Percentage of Plan Assets by Category
Plan Assets by Asset Category (as a percent)	43.00%	42.00%
United States Pension Plan of US Entity, Defined Benefit \| Debt Securities
Target Allocations by Asset Category
Target Allocations by Asset Category (as a percent)	48.00%
Percentage of Plan Assets by Category
Plan Assets by Asset Category (as a percent)	47.00%	49.00%
United States Pension Plan of US Entity, Defined Benefit \| Cash and Cash Equivalents
Target Allocations by Asset Category
Target Allocations by Asset Category (as a percent)	1.00%
Percentage of Plan Assets by Category
Plan Assets by Asset Category (as a percent)	1.00%	1.00%
United States Pension Plan of US Entity, Defined Benefit \| Property And Other
Target Allocations by Asset Category
Target Allocations by Asset Category (as a percent)	8.00%
Percentage of Plan Assets by Category
Plan Assets by Asset Category (as a percent)	9.00%	8.00%
Foreign Pension Plan, Defined Benefit
Target Allocations by Asset Category
Target Allocations by Asset Category (as a percent)	100.00%
Percentage of Plan Assets by Category
Plan Assets by Asset Category (as a percent)	100.00%	100.00%
Foreign Pension Plan, Defined Benefit \| Equity Securities
Target Allocations by Asset Category
Target Allocations by Asset Category (as a percent)	28.00%
Percentage of Plan Assets by Category
Plan Assets by Asset Category (as a percent)	27.00%	28.00%
Foreign Pension Plan, Defined Benefit \| Debt Securities
Target Allocations by Asset Category
Target Allocations by Asset Category (as a percent)	35.00%
Percentage of Plan Assets by Category
Plan Assets by Asset Category (as a percent)	38.00%	34.00%
Foreign Pension Plan, Defined Benefit \| Cash and Cash Equivalents
Target Allocations by Asset Category
Target Allocations by Asset Category (as a percent)	5.00%
Percentage of Plan Assets by Category
Plan Assets by Asset Category (as a percent)	2.00%	7.00%
Foreign Pension Plan, Defined Benefit \| Property And Other
Target Allocations by Asset Category
Target Allocations by Asset Category (as a percent)	32.00%
Percentage of Plan Assets by Category
Plan Assets by Asset Category (as a percent)	33.00%	31.00%

Pension Benefit Obligations - Asset Categories (Details) - Pension Plan, Defined Benefit - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Post-retirement plan
Fair values of plan assets	$ 1,463.5	$ 1,430.1
Cash and Cash Equivalents
Post-retirement plan
Fair values of plan assets	22.9	70.6
Global equity securities
Post-retirement plan
Fair values of plan assets	0.8	49.4
Domestic equity securities
Post-retirement plan
Fair values of plan assets	7.1	57.1
Diversified Funds
Post-retirement plan
Fair values of plan assets	212.8	223.1
Equity Funds
Post-retirement plan
Fair values of plan assets	467.9	362.0
Fixed Income Funds
Post-retirement plan
Fair values of plan assets	610.6	548.5
Hedge Funds
Post-retirement plan
Fair values of plan assets	110.1	62.5
Assets held by Insurance Company
Post-retirement plan
Fair values of plan assets	31.3	32.3
Other
Post-retirement plan
Fair values of plan assets		24.6
Level 1
Post-retirement plan
Fair values of plan assets	29.2	23.1
Level 1 \| Cash and Cash Equivalents
Post-retirement plan
Fair values of plan assets	13.1	14.3
Level 1 \| Domestic equity securities
Post-retirement plan
Fair values of plan assets	6.2
Level 1 \| Equity Funds
Post-retirement plan
Fair values of plan assets	6.4	5.1
Level 1 \| Fixed Income Funds
Post-retirement plan
Fair values of plan assets	3.5	3.7
Level 2
Post-retirement plan
Fair values of plan assets	1,394.1	1,392.9
Level 2 \| Cash and Cash Equivalents
Post-retirement plan
Fair values of plan assets	9.8	56.3
Level 2 \| Global equity securities
Post-retirement plan
Fair values of plan assets	0.8	49.4
Level 2 \| Domestic equity securities
Post-retirement plan
Fair values of plan assets	0.9	57.1
Level 2 \| Diversified Funds
Post-retirement plan
Fair values of plan assets	212.8	223.1
Level 2 \| Equity Funds
Post-retirement plan
Fair values of plan assets	461.5	356.9
Level 2 \| Fixed Income Funds
Post-retirement plan
Fair values of plan assets	607.1	544.8
Level 2 \| Hedge Funds
Post-retirement plan
Fair values of plan assets	69.9	48.4
Level 2 \| Assets held by Insurance Company
Post-retirement plan
Fair values of plan assets	31.3	32.3
Level 2 \| Other
Post-retirement plan
Fair values of plan assets		24.6
Level 3
Post-retirement plan
Fair values of plan assets	40.2	14.1
Level 3 \| Hedge Funds
Post-retirement plan
Fair values of plan assets	$ 40.2	$ 14.1	$ 13.6

Pension Benefit Obligations - Level 3 (Details) - Pension Plan, Defined Benefit - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Changes in the fair value of Level 3 assets
Fair value of plan assets at beginning of year	$ 1,430.1
Fair value of plan assets at end of year	1,463.5	$ 1,430.1
Hedge Funds
Changes in the fair value of Level 3 assets
Fair value of plan assets at beginning of year	62.5
Fair value of plan assets at end of year	110.1	62.5
Level 3
Changes in the fair value of Level 3 assets
Fair value of plan assets at beginning of year	14.1
Fair value of plan assets at end of year	40.2	14.1
Level 3 \| Hedge Funds
Changes in the fair value of Level 3 assets
Fair value of plan assets at beginning of year	14.1	13.6
Actual return on plan assets, relating to assets still held at reporting date	(0.2)	0.5
Transfer into / (out of) Level 3	26.3
Fair value of plan assets at end of year	$ 40.2	$ 14.1

Pension Benefit Obligations - Multiemployer (Details) - Multiemployer Pension Plans $ in Millions	12 Months Ended
	Sep. 30, 2017 USD ($) plan	Sep. 30, 2016 USD ($)
Multiemployer Pension Plans
Number of minimum construction-industry pension plans participated \| plan	200
Aggregate contributions to plans \| $	$ 48.8	$ 49.5

Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016	Oct. 17, 2014
Debt
Total debt	$ 3,896,400	$ 4,125,300
Less: Current portion of debt and short-term borrowings	(142,000)	(366,300)
Less: Unamortized debt issuance costs	(52,300)	(56,800)
Long-term debt	3,702,109	3,702,157
2014 Credit Agreement
Debt
Total debt	908,700	1,954,900
2014 Senior Notes
Debt
Total debt	1,600,000	1,600,000
2017 Senior Notes
Debt
Total debt	1,000,000
URS Senior Notes
Debt
Total debt	247,700	427,700	$ 1,000,000
Other Debt
Debt
Total debt	$ 140,000	$ 142,700

Debt - Scheduled Maturities (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
Scheduled maturities of debt:
2018	$ 142.0
2019	154.4
2020	122.6
2021	603.7
2022	256.7
Thereafter	2,617.0
Total debt	$ 3,896.4	$ 4,125.3

Debt - 2014 Credit Agreement (Details) $ in Millions			6 Months Ended	12 Months Ended
Debt - 2014 Credit Agreement (Details) $ in Millions	Sep. 29, 2016 USD ($)	Oct. 17, 2014 USD ($)	Mar. 31, 2017	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Term loan A
Debt agreements
Borrowing capacity	$ 185.0
2014 Credit Agreement \| Term loan B
Debt agreements
Borrowing capacity		$ 760.0
2014 Credit Agreement \| Revolving credit facility
Debt agreements
Borrowing capacity		1,050.0
Outstanding letters of credit				$ 58.1	$ 92.3
Remaining borrowing capacity under the credit facility				$ 991.9	$ 888.4
2014 Credit Agreement \| Line of Credit
Debt agreements
Borrowing capacity	$ 500.0
Increase in borrowing capacity		500.0
Consolidated leverage ratio	5.00		4.75	4.0
Consolidated interest coverage ratio				4.7
2014 Credit Agreement \| Term loan A
Debt agreements
Borrowing capacity		$ 1,925.0

Debt - 2014 and 2017 Senior Notes (Details) - USD ($)	Feb. 21, 2017	Oct. 06, 2014	Sep. 30, 2017
2014 Senior Notes \| The 2022 Notes
Debt
Principal amount		$ 800,000,000
Interest rate (as a percent)		5.75%
Fair value of debt instrument			$ 836,000,000
2014 Senior Notes \| The 2022 Notes \| Prior to October 15, 2017
Debt
Redemption price percentage		100.00%
Principal amount that can be redeemed (in percent)		35.00%
Redemption price (in percent)		105.75%
2014 Senior Notes \| The 2024 Notes
Debt
Principal amount		$ 800,000,000
Interest rate (as a percent)		5.875%
Fair value of debt instrument			884,000,000
2014 Senior Notes \| The 2024 Notes \| Prior to July 15 2024
Debt
Redemption price percentage		100.00%
2014 Senior Notes \| The 2024 Notes \| On or after July 15, 2024
Debt
Redemption price percentage		100.00%
2017 Senior Notes
Debt
Principal amount	$ 1,000,000,000
Interest rate (as a percent)	5.125%
Fair value of debt instrument			1,031,300,000
2017 Senior Notes \| Term loan A
Debt
Amount of debt redeemed	$ 600,000,000
2017 Senior Notes \| Term loan B
Debt
Amount of debt redeemed	127,600,000
2017 Senior Notes \| Revolving credit facility
Debt
Amount of debt redeemed	$ 250,000,000
2017 Senior Notes \| Prior to December 15, 2026
Debt
Redemption price percentage	100.00%
2017 Senior Notes \| Prior to March 15, 2020
Debt
Principal amount that can be redeemed (in percent)	35.00%
Redemption price (in percent)	105.125%
2017 Senior Notes \| On or after December 15, 2026
Debt
Redemption price percentage	100.00%
Registered Senior Notes 2017
Debt
Principal amount			999,074,000
Unregistered Senior Notes 2017
Debt
Principal amount			$ 926,000

Debt - URS Senior Notes and Other Debt (Details) - USD ($) $ in Millions		12 Months Ended
	Oct. 24, 2014	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Apr. 03, 2017	Sep. 29, 2016	Oct. 17, 2014
Debt
Debt		$ 3,896.4	$ 4,125.3
Effective interest rate		4.6%	4.4%	4.2%
Amortization of deferred debt issuance costs		$ 17.5	$ 30.9
Term loan A
Debt
Borrowing capacity						$ 185.0
URS Senior Notes
Debt
Redemption price (in percent)	101.00%
Amount of debt redeemed	$ 572.3				$ 179.2
Fair value of debt instrument		259.7
Debt		247.7	427.7				$ 1,000.0
URS Senior Notes \| 2017 URS Senor Notes
Debt
Interest rate (as a percent)							3.85%
URS Senior Notes \| 2022 URS Senior Notes
Debt
Interest rate (as a percent)							5.00%
Other Debt
Debt
Debt		140.0	142.7
Other Debt \| Unsecured \| Standby letter of credit
Debt
Outstanding letters of credit		445.7	$ 382.2
Remaining borrowing capacity under the credit facility		$ 502.3

Derivative Financial Instruments and Fair Value Measurements (Details) $ in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2017 AUD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 AUD ($)	Sep. 30, 2016 USD ($)
Derivative financial instruments
Payments			$ 21.0
Level 3
Derivative financial instruments
Contingent liability fair value			13.0		$ 39.0
Designated as Hedging Instrument \| Cash Flow Hedging \| Interest rate swap agreements
Derivative financial instruments
Losses Recognized in Income on Derivatives (Amount Excluded from Effectiveness Testing and Ineffective Portion)	$ 0.0
Designated as Hedging Instrument \| Cash Flow Hedging \| Interest Rate Swap June 2018
Derivative financial instruments
Notional Amount			$ 300.0		$ 300.0
Fixed Rate (as a percent)		1.63%	1.63%	1.63%	1.63%
Designated as Hedging Instrument \| Cash Flow Hedging \| Interest Rate Swap September 2018
Derivative financial instruments
Notional Amount			$ 300.0		$ 300.0
Fixed Rate (as a percent)		1.54%	1.54%	1.54%	1.54%
Designated as Hedging Instrument \| Cash Flow Hedging \| AUD \| Foreign currency forward contracts
Derivative financial instruments
Notional Amount		$ 15.1	$ 11.3	$ 58.6	$ 43.4

Leases (Details) - USD ($) $ in Millions	12 Months Ended
Leases (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Amounts payable under non-cancelable operating lease commitments
2018	$ 259.1
2019	214.8
2020	174.2
2021	139.7
2022	114.9
Thereafter	460.1
Total	1,362.8
Leases, additional disclosures
Rent expense for all leases	$ 265.9	$ 383.7	$ 395.9

Share-Based Payments - Incentive Plans (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Stock Incentive Plans
Compensation expense related to employer contributions to purchase AECOM stock under defined contribution plans, including the DCP	$ 32.9	$ 26.8	$ 13.3
Employee Stock Option
Stock Incentive Plans
Securities available for future issuance (in shares)	13,600,000
Expiration term of unexercised options	7 years
Number of Options
Balance at the beginning of the period (in shares)	900,000	1,300,000	1,600,000
Exercised (in shares)	(200,000)	(400,000)	(300,000)
Balance at the end of the period (in shares)	700,000	900,000	1,300,000
Exercisable at the end of the period (in shares)	100,000	300,000	700,000
Stock options, Weighted Average Exercise Price
Balance at the beginning of the period (in dollars per share)	$ 30.36	$ 28.26	$ 27.69
Exercised (in dollars per share)	26.42	23.96	24.98
Balance at the end of the period (in dollars per share)	31.11	30.36	28.26
Exercisable at the end of the period (in dollars per share)	$ 27.79	$ 26.99	$ 25.04

Share-Based Payments - Exercisable Options (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Compensation expense
Allocated Share-based Compensation Expense	$ 83.8	$ 73.4	$ 112.2
Unrecognized compensation expense	$ 96.8	91.8
Vesting period	3 years
URS \| Acquisition And Integration Expenses
Compensation expense
Compensation to settle accelerated equity awards			43.9
Accelerated equity award - Company stock			17.6
Accelerated equity award - cash			26.3
Employee Stock Option
Options Outstanding
Number outstanding as of end of period (in shares)	700,000
Weighted Average Remaining Contractual Life	5 years 7 months 10 days
Weighted Average Exercise Price (in dollars per share)	$ 31.11
Aggregate Intrinsic Value (in millions)	$ 4.2
Options Exercisable
Number Exercisable at the end of the period (in shares)	100,000
Weighted Average Remaining Contractual Life	3 months 7 days
Weighted Average Exercise Price (in dollars per share)	$ 27.79
Stock Incentive Plans, additional disclosures
Remaining contractual life of options outstanding, low end of range	2 months 9 days
Remaining contractual life of options outstanding, high end of range	6 years 5 months 5 days
Aggregate intrinsic value of stock options exercised	$ 1.2	$ 0.6	$ 2.1
Compensation expense
Number of stock options granted during the period	0	0
Performance Earnings Program
Compensation expense
Weighted average grant-date fair value of stock options granted (in dollars per share)	$ 38.15	$ 29.91	$ 32.32
Performance period over which objectives must be met to qualify for an award grant	3 years
Restricted Stock Units (RSUs)
Compensation expense
Weighted average grant-date fair value of stock options granted (in dollars per share)	$ 37.96	$ 29.82	31.05
Restricted Stock Units (RSUs) \| URS
Compensation expense
Weighted average grant-date fair value of stock options granted (in dollars per share)			$ 30.04
Number of stock options granted during the period			2,600,000
$27.54 - $28.44
Information concerning outstanding and exercisable options
Exercise price, low end of range (in dollars per share)	27.54
Exercise price, high end of range (in dollars per share)	$ 28.44
$27.54 - $28.44 \| Employee Stock Option
Options Outstanding
Number outstanding as of end of period (in shares)	100,000
Weighted Average Remaining Contractual Life	3 months 7 days
Weighted Average Exercise Price (in dollars per share)	$ 27.79
Aggregate Intrinsic Value (in millions)	$ 0.9
Options Exercisable
Number Exercisable at the end of the period (in shares)	100,000
Weighted Average Remaining Contractual Life	3 months 7 days
Weighted Average Exercise Price (in dollars per share)	$ 27.79
$31.62
Options Outstanding
Weighted Average Exercise Price (in dollars per share)	$ 31.62
$31.62 \| Employee Stock Option
Options Outstanding
Number outstanding as of end of period (in shares)	600,000
Weighted Average Remaining Contractual Life	6 years 5 months 5 days
Weighted Average Exercise Price (in dollars per share)	$ 31.62
Aggregate Intrinsic Value (in millions)	$ 3.3

Income Taxes - Tax (Benefit) Expense (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Income Taxes
Income (loss) from domestic operations before income tax expense									$ 322,200	$ 51,600	$ (214,600)
Income from foreign operations before income tax expense									107,000	74,000	63,100
Current:
Federal									10,300	33,700	(67,100)
State									17,900	12,400	2,600
Foreign									29,300	26,100	37,200
Total current income tax expense (benefit)									57,500	72,200	(27,300)
Deferred:
Federal									(8,300)	(63,400)	(44,200)
State									10,400	(5,400)	1,200
Foreign									(51,900)	(41,300)	(10,000)
Total deferred income tax (benefit) expense									(49,856)	(110,122)	(53,034)
Total income tax expense (benefit)	$ 6,200	$ 12,100	$ (35,400)	$ 24,800	$ (14,300)	$ (35,100)	$ 12,200	$ (700)	$ 7,706	$ (37,917)	$ (80,237)

Income Taxes - Federal Rate Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Income Taxes
Benefit recognized expired incentives and credits										$ 10,100	$ 19,400
Major elements contributing to the difference between the U.S. federal statutory rate of 35.0% and the effective tax rate
Tax at federal statutory rate									$ 150,300	43,900	(53,000)
State income tax, net of federal benefit									24,300	5,600	(2,300)
Income tax credits and incentives									(56,800)	(24,600)	(21,200)
Valuation allowance									(51,200)	(54,800)	30,000
Exclusion of tax on non-controlling interests									(28,200)	(24,700)	(29,300)
Foreign tax rate differential									(19,200)	(19,700)	(24,800)
Tax exempt income									(17,900)	(17,600)	(13,200)
Foreign residual income										17,800	20,100
Foreign residual income									(9,200)
Change in uncertain tax positions									9,500	(5,000)	6,600
Nondeductible costs									5,800	6,100	2,800
Other items, net									300	500	1,200
Change in tax rates										34,600
Nondeductible transaction costs											2,800
Total income tax expense (benefit)	$ 6,200	$ 12,100	$ (35,400)	$ 24,800	$ (14,300)	$ (35,100)	$ 12,200	$ (700)	$ 7,706	$ (37,917)	$ (80,237)
Major elements contributing to the difference between the U.S. federal statutory rate of 35.0% and the effective tax rate
Federal statutory rate (as a percent)									35.00%	35.00%	35.00%
State income tax, net of federal benefit (as a percent)									5.70%	4.50%	1.50%
Income tax credits and incentive (as a percent)									(13.20%)	(19.60%)	14.00%
Valuation allowance (as a percent)									(11.90%)	(43.60%)	(19.80%)
Exclusion of tax on non-controlling interests (as a percent)									(6.60%)	(19.70%)	19.30%
Foreign tax rate differential (as a percent)									(4.50%)	(15.70%)	16.40%
Tax exempt income (as a percent)									(4.20%)	(14.00%)	8.70%
Foreign residual income (as a percent)									(2.10%)		(13.30%)
Foreign residual income (as a percent)										14.20%
Change in uncertain tax positions (as a percent)									2.20%	(4.00%)	(4.30%)
Nondeductible costs (as a percent)									1.40%	4.80%	(1.80%)
Other items, net (as a percent)										0.30%	(0.90%)
Change in tax rates (as a percent)										27.60%
Nondeductible transaction costs (as a percent)											(1.80%)
Total income tax expense (as a percent)									1.80%	(30.20%)	53.00%

Income Taxes - Deferred tax (Details) $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended
Income Taxes - Deferred tax (Details) $ in Millions	Oct. 31, 2014 USD ($)	Jun. 30, 2017 USD ($) subsidiary	Jun. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Deferred tax assets:
Compensation and benefit accruals not currently deductible				$ 144.2	$ 150.5
Net operating loss carryforwards				338.2	378.0
Self insurance reserves				23.8	24.7
Research and experimentation and other tax credits				167.5	125.3
Pension liability				142.1	180.9
Accrued liabilities				160.7	221.0
Other				25.0	4.3
Total deferred tax assets				1,001.5	1,084.7
Deferred tax liabilities:
Unearned revenue				(190.8)	(212.6)
Depreciation and amortization				(158.6)	(113.0)
Acquired intangible assets				(121.7)	(155.5)
Investment in subsidiaries				(241.2)	(261.4)
Total deferred tax liabilities				(712.3)	(742.5)
Valuation allowance				(138.4)	(183.8)
Net deferred tax assets				150.8	158.4
Income Taxes, additional disclosures
Remaining gross tax asset exclusive of tax liabilities realized				863.1
Change in valuation allowance				(45.3)
Foreign net operating loss carryforwards				4.1
Benefits related to excess foreign tax credits expected to be realized				25.2
Gross book-tax differences from non-U.S. subsidiaries				1,700.0
Deferred tax liability of foreign subsidiaries				77.0	113.2
Liability for unrecognized tax benefits, including potential interest and penalties, net of related tax benefit				109.5	$ 96.8
Unrecognized tax benefits that would be included in the effective tax rate if recognized				86.1
United Kingdom
Income Taxes, additional disclosures
Change in valuation allowance	$ 92.8	$ (23.3)		(59.9)
Australia
Income Taxes, additional disclosures
Change in valuation allowance	2.9		$ (12.9)
Canada
Income Taxes, additional disclosures
Change in valuation allowance	22.5
United States
Income Taxes, additional disclosures
Change in valuation allowance	$ 9.3
Europe
Income Taxes, additional disclosures
Number of subsidiaries recapitalized \| subsidiary		1
Benefit due to reinvesting portion of undistributed earnings		$ 21.2
California Franchise Tax Board \| Enterprise Zone Tax Credits
Income Taxes, additional disclosures
Unused tax credits				6.6
Employee share-based payment adjustment
Income Taxes, additional disclosures
Net operating loss carryforwards						$ 3.8
Federal
Income Taxes, additional disclosures
Net operating loss carryforwards				368.8
Federal \| Research and development
Income Taxes, additional disclosures
Unused tax credits				83.5
State
Income Taxes, additional disclosures
Net operating loss carryforwards				899.6
State \| Research and development
Income Taxes, additional disclosures
Unused tax credits				21.8
Foreign
Income Taxes, additional disclosures
Net operating loss carryforwards				843.8
Unused tax credits				$ 74.8

Income Taxes - Gross Unrecognized (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Reconciliation of the beginning and ending amount of gross unrecognized tax benefits
Balance at the beginning of the year	$ 87.9	$ 95.2
Gross increase in current period's tax positions	10.8	7.6
Gross increase in prior years' tax positions	5.3	5.2
Gross decrease in prior years' tax positions		(16.6)
Decrease due to settlement with tax authorities	(1.0)	(3.2)
Decrease due to lapse of statute of limitations	(1.1)	(1.8)
Gross change due to foreign exchange fluctuations	0.2	1.5
Balance at the end of the year	102.1	87.9
Income Taxes, additional disclosures
Accrued interest, excluding any related income tax benefits	15.1	12.5
Accrued penalties, excluding any related income tax benefits	$ 4.1	$ 2.6

Earnings Per Share (Details) - shares shares in Thousands	3 Months Ended								12 Months Ended
Earnings Per Share (Details) - shares shares in Thousands	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share
Antidilutive potential common shares excluded in computation of diluted loss per share											1,700
Denominator for basic earnings per share (in shares)	157,500	155,800	155,400	154,300	156,300	154,900	154,300	153,600	155,728	154,772	149,605
Potential common shares (in shares)									3,400	1,300
Denominator for diluted earnings per share (in shares)	161,100	158,800	158,700	158,000	157,900	156,200	155,400	153,600	159,135	156,073	149,605

Other Financial Information (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Accrued expenses and other current liabilities
Accrued salaries and benefits	$ 1,018,500	$ 964,900
Accrued contract costs	911,900	1,009,800
Other accrued expenses	315,100	410,100
Total accrued expenses	2,245,519	2,384,815
Additional information
Accounts receivable-net	5,127,743	4,531,460
Accelerated recovery of pension entitlement
Additional information
Accounts receivable-net	50,000
Professional liability accrual
Accrued expenses and other current liabilities
Accrued contract costs	$ 547,900	$ 611,000

Reclassifications out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Accumulated balances
Balance at the beginning of the period	$ (857,582)	$ (635,100)	$ (356,600)
Other comprehensive (loss) income before reclassification	141,400	(233,900)	(289,800)
Amounts reclassified from accumulated other comprehensive loss	15,500	11,400	11,300
Balance at the end of the period	(700,661)	(857,582)	(635,100)
Pension Related Adjustments
Accumulated balances
Balance at the beginning of the period	(368,900)	(204,000)	(217,000)
Other comprehensive (loss) income before reclassification	73,800	(171,500)	5,800
Amounts reclassified from accumulated other comprehensive loss	13,200	6,600	7,200
Balance at the end of the period	(281,900)	(368,900)	(204,000)
Foreign Currency Translation Adjustments
Accumulated balances
Balance at the beginning of the period	(483,700)	(420,100)	(137,800)
Other comprehensive (loss) income before reclassification	65,300	(63,600)	(282,300)
Balance at the end of the period	(418,400)	(483,700)	(420,100)
Loss on Derivative Instruments
Accumulated balances
Balance at the beginning of the period	(5,000)	(11,000)	(1,800)
Other comprehensive (loss) income before reclassification	2,300	1,200	(13,300)
Amounts reclassified from accumulated other comprehensive loss	2,300	4,800	4,100
Balance at the end of the period	$ (400)	$ (5,000)	$ (11,000)

Commitments and Contingencies (Details) - USD ($)			1 Months Ended
Commitments and Contingencies (Details) - USD ($)	Apr. 17, 2017	Mar. 09, 2017	Sep. 30, 2016	Dec. 31, 2014	Sep. 30, 2017
Design build contractor
Commitments and Contingencies
Damages claimed, value	$ 70,000,000
URS
Commitments and Contingencies
Damages claimed, value		$ 8,900,000
DOE Deactivation, Demolition, And Removal Project \| WGI Ohio and DOE \| Minimum
Commitments and Contingencies
Cost-reimbursement at risk					$ 106,000,000
DOE Deactivation, Demolition, And Removal Project \| WGI Ohio and DOE \| Maximum
Commitments and Contingencies
Cost-reimbursement at risk					146,000,000
DOE Deactivation, Demolition, And Removal Project \| WGI Ohio
Commitments and Contingencies
Claim to DOE, including additional fees				$ 103,000,000
Possible costs which may exceed contracted amounts				$ 100,000,000
DOE Deactivation, Demolition, And Removal Project \| WGI Ohio \| Minimum
Commitments and Contingencies
Cost-reimbursement at risk					146,000,000
DOE Deactivation, Demolition, And Removal Project \| New York State \| Department of Energy \| Maximum
Commitments and Contingencies
Cost-reimbursement at risk					106,000,000
Standby letters of credit
Commitments and Contingencies
Contingency liability					503,800,000
Surety Bond
Commitments and Contingencies
Contingency liability					$ 5,700,000,000
New York Department of Environmental Conservation \| AECOM USA, Inc. \| Minimum
Commitments and Contingencies
Damages claimed, value			$ 100,000

Reportable Segments and Geographic Information - Segments (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2017 USD ($) segment	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)
Summarized financial information concerning the Company's reportable segments
Number of reportable segments \| segment									4
Cost of revenue.	$ 4,686,300	$ 4,386,300	$ 4,258,800	$ 4,188,300	$ 4,175,900	$ 4,237,500	$ 4,197,800	$ 4,156,800	$ 17,519,682	$ 16,768,001	$ 17,454,692
Revenue	4,856,400	4,561,500	4,427,200	4,358,300	4,323,100	4,408,800	4,381,200	4,297,700	18,203,402	17,410,825	17,989,880
Gross profit	170,100	175,200	168,400	170,000	147,200	171,300	183,400	140,900	683,720	642,824	535,188
Equity in earnings of joint ventures	31,900	66,500	21,800	21,400	21,200	18,500	39,100	25,200	141,582	104,032	106,245
General and administrative expenses	(36,900)	(34,000)	(29,900)	(32,600)	(28,200)	(28,700)	(29,500)	(28,700)	(133,309)	(115,088)	(113,975)
Acquisition and integration expenses	(3,300)		(20,000)	(15,400)	(71,200)	(50,700)	(50,700)	(41,000)	(38,709)	(213,642)	(398,440)
Gain (loss) on disposal activities			600				(1,600)	(41,000)	572	(42,589)
Operating income	161,800	$ 207,700	$ 140,900	$ 143,400	69,000	$ 110,400	$ 140,700	$ 55,400	653,856	375,537	129,018
Segment assets	14,396,956				13,669,936				$ 14,396,956	$ 13,669,936	$ 14,014,300
Gross profit as a % of revenue									3.80%	3.70%	3.00%
Corporate
Summarized financial information concerning the Company's reportable segments
General and administrative expenses									$ (124,700)	$ (109,100)	$ (109,700)
Acquisition and integration expenses									(38,700)	(213,600)	(398,400)
Operating income									(163,400)	(322,700)	(508,100)
Segment assets	386,200				586,200				386,200	586,200	498,100
DCS
Summarized financial information concerning the Company's reportable segments
Revenue									7,566,800	7,655,800	7,962,900
Gross profit									394,800	382,500	299,300
Equity in earnings of joint ventures									16,400	8,900	6,600
Gain (loss) on disposal activities									600
Operating income									411,800	391,400	305,900
Segment assets	6,992,600				6,655,700				$ 6,992,600	$ 6,655,700	$ 7,118,200
Gross profit as a % of revenue									5.20%	5.00%	3.80%
CS
Summarized financial information concerning the Company's reportable segments
Revenue									$ 7,295,600	$ 6,371,100	$ 6,539,300
Gross profit									92,900	25,400	35,900
Equity in earnings of joint ventures									22,400	18,200	23,000
Gain (loss) on disposal activities										(42,600)
Operating income									115,300	1,000	58,900
Segment assets	4,114,500				3,556,200				$ 4,114,500	$ 3,556,200	$ 3,382,400
Gross profit as a % of revenue									1.30%	0.40%	0.50%
MS
Summarized financial information concerning the Company's reportable segments
Revenue									$ 3,341,000	$ 3,383,900	$ 3,487,700
Gross profit									196,000	234,900	200,000
Equity in earnings of joint ventures									45,100	76,900	76,600
Operating income									241,100	311,800	276,600
Segment assets	2,704,600				2,692,700				$ 2,704,600	$ 2,692,700	$ 2,903,900
Gross profit as a % of revenue									5.90%	6.90%	5.70%
MS \| Restatement Adjustment
Summarized financial information concerning the Company's reportable segments
Cost of revenue.										$ 124,000	$ 130,000
Revenue										130,000	137,000
ACAP
Summarized financial information concerning the Company's reportable segments
Equity in earnings of joint ventures									$ 57,700
General and administrative expenses									(8,700)	(6,000)	(4,300)
Operating income									49,000	(6,000)	(4,300)
Segment assets	$ 199,100				$ 179,100				$ 199,100	$ 179,100	$ 111,700

Reportable Segments and Geographic Information - Geographic (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Geographic Information
Revenue	$ 4,856,400	$ 4,561,500	$ 4,427,200	$ 4,358,300	$ 4,323,100	$ 4,408,800	$ 4,381,200	$ 4,297,700	$ 18,203,402	$ 17,410,825	$ 17,989,880
Long-Lived Assets	7,543,400				7,554,500				7,543,400	7,554,500	7,768,200
United States
Geographic Information
Revenue									13,042,600	12,567,000	12,599,600
Long-Lived Assets	4,779,000				4,763,900				4,779,000	4,763,900	4,852,500
Asia Pacific
Geographic Information
Revenue									1,352,700	1,278,300	1,385,300
Long-Lived Assets	382,900				394,000				382,900	394,000	426,400
Canada
Geographic Information
Revenue									1,159,900	866,500	1,308,300
Long-Lived Assets	600,400				615,700				600,400	615,700	641,000
Europe
Geographic Information
Revenue									1,869,900	1,904,200	1,796,900
Long-Lived Assets	1,362,800				1,368,400				1,362,800	1,368,400	1,496,200
Other foreign countries
Geographic Information
Revenue									778,300	794,800	899,800
Long-Lived Assets	$ 418,300				$ 412,500				$ 418,300	$ 412,500	$ 352,100

Major Clients (Details) - Sales Revenue, Services, Net - Customer Concentration Risk	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Percentage of total revenue
Period for which criteria of threshold percentage for disclosure not met in past	5 years
Maximum
Percentage of total revenue
Percentage of revenue accounted for by no other single client (as a percent)	10.00%
Agencies of U.S. Federal Government
Percentage of total revenue
Concentration (as a percent)	22.00%	23.00%	24.00%
Agencies of U.S. Federal Government \| MS
Percentage of total revenue
Concentration (as a percent)	3.00%	3.00%	2.00%

Quarterly Financial Information-Unaudited (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Quarterly Financial Information-Unaudited
Revenue	$ 4,856,400	$ 4,561,500	$ 4,427,200	$ 4,358,300	$ 4,323,100	$ 4,408,800	$ 4,381,200	$ 4,297,700	$ 18,203,402	$ 17,410,825	$ 17,989,880
Cost of revenue	4,686,300	4,386,300	4,258,800	4,188,300	4,175,900	4,237,500	4,197,800	4,156,800	17,519,682	16,768,001	17,454,692
Gross profit	170,100	175,200	168,400	170,000	147,200	171,300	183,400	140,900	683,720	642,824	535,188
Equity in earnings of joint ventures	31,900	66,500	21,800	21,400	21,200	18,500	39,100	25,200	141,582	104,032	106,245
General and administrative expenses	(36,900)	(34,000)	(29,900)	(32,600)	(28,200)	(28,700)	(29,500)	(28,700)	(133,309)	(115,088)	(113,975)
Acquisition and integration expenses	(3,300)		(20,000)	(15,400)	(71,200)	(50,700)	(50,700)	(41,000)	(38,709)	(213,642)	(398,440)
Gain (loss) on disposal activities			600				(1,600)	(41,000)	572	(42,589)
Income from operations	161,800	207,700	140,900	143,400	69,000	110,400	140,700	55,400	653,856	375,537	129,018
Other income (expense)	2,500	2,100	1,300	800	2,900	1,500	800	3,000	6,636	8,180	19,139
Interest expense	(54,300)	(61,600)	(61,800)	(53,600)	(73,300)	(62,600)	(62,700)	(59,500)	(231,310)	(258,162)	(299,627)
Income (loss) before income tax (benefit) expense	110,000	148,200	80,400	90,600	(1,400)	49,300	78,800	(1,100)	429,182	125,555	(151,470)
Income tax (benefit) expense	6,200	12,100	(35,400)	24,800	(14,300)	(35,100)	12,200	(700)	7,706	(37,917)	(80,237)
Net income (loss)	103,800	136,100	115,800	65,800	12,900	84,400	66,600	(400)	421,476	163,472	(71,233)
Noncontrolling interests in income of consolidated subsidiaries, net of tax	(15,300)	(34,800)	(13,400)	(18,600)	(5,700)	(17,000)	(24,700)	(20,000)	(82,086)	(67,363)	(83,612)
Net income (loss) attributable to AECOM	$ 88,500	$ 101,300	$ 102,400	$ 47,200	$ 7,200	$ 67,400	$ 41,900	$ (20,400)	$ 339,390	$ 96,109	$ (154,845)
Net (loss) income attributable to AECOM per share:
Basic (in dollars per share)	$ 0.56	$ 0.65	$ 0.66	$ 0.31	$ 0.05	$ 0.44	$ 0.27	$ (0.13)	$ 2.18	$ 0.62	$ (1.04)
Diluted (in dollars per share)	$ 0.55	$ 0.64	$ 0.65	$ 0.30	$ 0.05	$ 0.43	$ 0.27	$ (0.13)	$ 2.13	$ 0.62	$ (1.04)
Weighted average shares outstanding:
Basic (in shares)	157,500	155,800	155,400	154,300	156,300	154,900	154,300	153,600	155,728	154,772	149,605
Diluted (in shares)	161,100	158,800	158,700	158,000	157,900	156,200	155,400	153,600	159,135	156,073	149,605

Condensed Consolidating Financial Information - Debt (Details)	Oct. 06, 2014
Condensed Consolidating Financial Information
Ownership of directly and indirectly owned subsidiaries (as a percent)	100.00%

Condensed Consolidating Financial Information - Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
CURRENT ASSETS:
Total cash and cash equivalents	$ 802,362	$ 692,145	$ 683,893	$ 574,188
Accounts receivable-net	5,127,743	4,531,460
Prepaid expenses and other current assets	696,718	730,101
Income taxes receivable	55,399	47,065
TOTAL CURRENT ASSETS	6,682,222	6,000,771
PROPERTY AND EQUIPMENT-NET	621,357	644,992
DEFERRED TAX ASSETS-NET	171,331	171,508
INVESTMENTS IN UNCONSOLIDATED JOINT VENTURES	364,223	330,485
GOODWILL	5,992,881	5,823,843	5,820,700
INTANGIBLE ASSETS-NET	415,096	479,439
OTHER NON-CURRENT ASSETS	149,846	218,898
TOTAL ASSETS	14,396,956	13,669,936	14,014,300
CURRENT LIABILITIES:
Short-term debt	1,221	26,303
Accounts payable	2,249,872	1,910,915
Accrued expenses and other current liabilities	2,245,519	2,384,815
Accrued taxes payable	38,176	10,774
Billings in excess of costs on uncompleted contracts	902,812	631,928
Current portion of long-term debt	140,779	340,021
TOTAL CURRENT LIABILITIES	5,578,379	5,304,756
OTHER LONG-TERM LIABILITIES	881,300	1,097,400
DEFERRED TAX LIABILITY-NET	20,515	13,097
LONG-TERM DEBT	3,702,109	3,702,157
TOTAL LIABILITIES	10,182,270	10,117,447
TOTAL AECOM STOCKHOLDERS' EQUITY	3,996,126	3,366,921
Noncontrolling interests	218,560	185,568
TOTAL STOCKHOLDERS' EQUITY	4,214,686	3,552,489	3,630,943	2,272,480
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	14,396,956	13,669,936
Reportable Legal Entities \| Parent
CURRENT ASSETS:
Total cash and cash equivalents	32,600	1,800	1,300	33,400
Intercompany receivable	723,600	760,700
Prepaid expenses and other current assets	67,500	98,700
Income taxes receivable	4,300	28,700
TOTAL CURRENT ASSETS	828,000	889,900
PROPERTY AND EQUIPMENT-NET	160,200	169,300
DEFERRED TAX ASSETS-NET	239,700	265,200
INVESTMENTS IN CONSOLIDATED JOINT VENTURES AND SUBSIDIARIES	6,606,200	6,031,700
INVESTMENTS IN UNCONSOLIDATED JOINT VENTURES	7,200	700
OTHER NON-CURRENT ASSETS	8,700	8,200
TOTAL ASSETS	7,850,000	7,365,000
CURRENT LIABILITIES:
Short-term debt	1,100	3,100
Accounts payable	33,800	45,800
Accrued expenses and other current liabilities	92,200	201,200
Intercompany payable	149,200	114,100
Billings in excess of costs on uncompleted contracts	3,400
Current portion of long-term debt	110,900	108,200
TOTAL CURRENT LIABILITIES	390,600	472,400
OTHER LONG-TERM LIABILITIES	102,300	115,700
NOTE PAYABLE INTERCOMPANY-NON CURRENT	100
LONG-TERM DEBT	3,366,900	3,411,200
TOTAL LIABILITIES	3,859,900	3,999,300
TOTAL AECOM STOCKHOLDERS' EQUITY	3,990,100	3,365,700
TOTAL STOCKHOLDERS' EQUITY	3,990,100	3,365,700
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	7,850,000	7,365,000
Reportable Legal Entities \| Guarantor Subsidiaries
CURRENT ASSETS:
Total cash and cash equivalents	251,600	183,700	162,500	85,800
Accounts receivable-net	2,159,200	2,034,000
Intercompany receivable	90,900	151,700
Prepaid expenses and other current assets	338,400	336,200
TOTAL CURRENT ASSETS	2,840,100	2,705,600
PROPERTY AND EQUIPMENT-NET	207,100	236,500
DEFERRED TAX ASSETS-NET	55,200
INVESTMENTS IN CONSOLIDATED JOINT VENTURES AND SUBSIDIARIES	2,865,000	2,681,500
INVESTMENTS IN UNCONSOLIDATED JOINT VENTURES	50,300	48,600
GOODWILL	3,318,600	3,286,600
INTANGIBLE ASSETS-NET	271,600	334,000
OTHER NON-CURRENT ASSETS	17,600	71,500
TOTAL ASSETS	9,625,500	9,364,300
CURRENT LIABILITIES:
Short-term debt		7,300
Accounts payable	1,023,700	907,000
Accrued expenses and other current liabilities	1,112,900	1,137,100
Intercompany payable	787,500	857,900
Billings in excess of costs on uncompleted contracts	313,100	237,500
Current portion of long-term debt	14,900	222,100
TOTAL CURRENT LIABILITIES	3,252,100	3,368,900
OTHER LONG-TERM LIABILITIES	285,700	349,300
DEFERRED TAX LIABILITY-NET		236,600
LONG-TERM DEBT	281,600	273,400
TOTAL LIABILITIES	3,819,400	4,228,200
TOTAL AECOM STOCKHOLDERS' EQUITY	5,806,100	5,136,100
TOTAL STOCKHOLDERS' EQUITY	5,806,100	5,136,100
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	9,625,500	9,364,300
Reportable Legal Entities \| Non-Guarantor Subsidiaries
CURRENT ASSETS:
Total cash and cash equivalents	518,200	506,600	$ 520,100	$ 455,000
Accounts receivable-net	2,968,500	2,497,500
Intercompany receivable	181,400	152,000
Prepaid expenses and other current assets	290,800	295,200
Income taxes receivable	51,100	18,400
TOTAL CURRENT ASSETS	4,010,000	3,469,700
PROPERTY AND EQUIPMENT-NET	254,100	239,200
DEFERRED TAX ASSETS-NET	171,000	129,800
INVESTMENTS IN UNCONSOLIDATED JOINT VENTURES	306,700	281,200
GOODWILL	2,674,300	2,537,200
INTANGIBLE ASSETS-NET	143,500	145,400
OTHER NON-CURRENT ASSETS	123,600	139,200
TOTAL ASSETS	7,683,200	6,941,700
CURRENT LIABILITIES:
Short-term debt	100	15,900
Accounts payable	1,192,400	958,100
Accrued expenses and other current liabilities	1,040,400	1,046,500
Accrued taxes payable	38,200	10,800
Intercompany payable	161,400	208,800
Billings in excess of costs on uncompleted contracts	586,300	394,400
Current portion of long-term debt	15,000	9,700
TOTAL CURRENT LIABILITIES	3,033,800	2,644,200
OTHER LONG-TERM LIABILITIES	493,300	632,400
DEFERRED TAX LIABILITY-NET	315,100
NOTE PAYABLE INTERCOMPANY-NON CURRENT	467,200	563,500
LONG-TERM DEBT	53,600	17,600
TOTAL LIABILITIES	4,363,000	3,857,700
TOTAL AECOM STOCKHOLDERS' EQUITY	3,101,600	2,898,400
Noncontrolling interests	218,600	185,600
TOTAL STOCKHOLDERS' EQUITY	3,320,200	3,084,000
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	7,683,200	6,941,700
Eliminations
CURRENT ASSETS:
Intercompany receivable	(995,900)	(1,064,400)
TOTAL CURRENT ASSETS	(995,900)	(1,064,400)
DEFERRED TAX ASSETS-NET	(294,600)	(223,500)
INVESTMENTS IN CONSOLIDATED JOINT VENTURES AND SUBSIDIARIES	(9,471,200)	(8,713,200)
TOTAL ASSETS	(10,761,700)	(10,001,100)
CURRENT LIABILITIES:
Intercompany payable	(1,098,100)	(1,180,800)
TOTAL CURRENT LIABILITIES	(1,098,100)	(1,180,800)
DEFERRED TAX LIABILITY-NET	(294,600)	(223,500)
NOTE PAYABLE INTERCOMPANY-NON CURRENT	(467,300)	(563,500)
TOTAL LIABILITIES	(1,860,000)	(1,967,800)
TOTAL AECOM STOCKHOLDERS' EQUITY	(8,901,700)	(8,033,300)
TOTAL STOCKHOLDERS' EQUITY	(8,901,700)	(8,033,300)
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ (10,761,700)	$ (10,001,100)

Condensed Consolidating Financial Information - Operations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Condensed Consolidating Statements of Operations
Revenue	$ 4,856,400	$ 4,561,500	$ 4,427,200	$ 4,358,300	$ 4,323,100	$ 4,408,800	$ 4,381,200	$ 4,297,700	$ 18,203,402	$ 17,410,825	$ 17,989,880
Cost of revenue	4,686,300	4,386,300	4,258,800	4,188,300	4,175,900	4,237,500	4,197,800	4,156,800	17,519,682	16,768,001	17,454,692
Gross profit	170,100	175,200	168,400	170,000	147,200	171,300	183,400	140,900	683,720	642,824	535,188
Equity in earnings of joint ventures	31,900	66,500	21,800	21,400	21,200	18,500	39,100	25,200	141,582	104,032	106,245
General and administrative expenses	(36,900)	(34,000)	(29,900)	(32,600)	(28,200)	(28,700)	(29,500)	(28,700)	(133,309)	(115,088)	(113,975)
Acquisition and integration expenses	(3,300)		(20,000)	(15,400)	(71,200)	(50,700)	(50,700)	(41,000)	(38,709)	(213,642)	(398,440)
Gain (loss) on disposal activities			600				(1,600)	(41,000)	572	(42,589)
Income from operations	161,800	207,700	140,900	143,400	69,000	110,400	140,700	55,400	653,856	375,537	129,018
Other income (expense)	2,500	2,100	1,300	800	2,900	1,500	800	3,000	6,636	8,180	19,139
Interest (expense) income	(54,300)	(61,600)	(61,800)	(53,600)	(73,300)	(62,600)	(62,700)	(59,500)	(231,310)	(258,162)	(299,627)
Income (loss) before income tax (benefit) expense	110,000	148,200	80,400	90,600	(1,400)	49,300	78,800	(1,100)	429,182	125,555	(151,470)
Income tax (benefit) expense	6,200	12,100	(35,400)	24,800	(14,300)	(35,100)	12,200	(700)	7,706	(37,917)	(80,237)
Net income (loss)	103,800	136,100	115,800	65,800	12,900	84,400	66,600	(400)	421,476	163,472	(71,233)
Noncontrolling interests in income of consolidated subsidiaries, net of tax	(15,300)	(34,800)	(13,400)	(18,600)	(5,700)	(17,000)	(24,700)	(20,000)	(82,086)	(67,363)	(83,612)
Net income (loss) attributable to AECOM	$ 88,500	$ 101,300	$ 102,400	$ 47,200	$ 7,200	$ 67,400	$ 41,900	$ (20,400)	339,390	96,109	(154,845)
Reportable Legal Entities \| Parent
Condensed Consolidating Statements of Operations
Equity in earnings from subsidiaries									439,300	437,400	321,300
General and administrative expenses									(124,700)	(114,000)	(112,200)
Acquisition and integration expenses									(38,700)	(213,600)	(346,900)
Income from operations									275,900	109,800	(137,800)
Other income (expense)									2,200	800	5,100
Interest (expense) income									(203,700)	(231,700)	(275,400)
Income (loss) before income tax (benefit) expense									74,400	(121,100)	(408,100)
Income tax (benefit) expense									(264,900)	(217,300)	(253,300)
Net income (loss)									339,300	96,200	(154,800)
Net income (loss) attributable to AECOM									339,300	96,200	(154,800)
Reportable Legal Entities \| Guarantor Subsidiaries
Condensed Consolidating Statements of Operations
Revenue									9,367,100	9,227,500	8,749,500
Cost of revenue									9,000,300	8,909,400	8,486,400
Gross profit									366,800	318,100	263,100
Equity in earnings from subsidiaries									217,200	243,600	198,900
Equity in earnings of joint ventures									25,400	27,300	20,000
General and administrative expenses										(1,100)	(1,800)
Acquisition and integration expenses											(51,500)
Income from operations									609,400	587,900	428,700
Other income (expense)									31,700	34,700	34,900
Interest (expense) income									(26,500)	(23,600)	(20,400)
Income (loss) before income tax (benefit) expense									614,600	599,000	443,200
Income tax (benefit) expense									175,800	114,300	66,700
Net income (loss)									438,800	484,700	376,500
Net income (loss) attributable to AECOM									438,800	484,700	376,500
Reportable Legal Entities \| Non-Guarantor Subsidiaries
Condensed Consolidating Statements of Operations
Revenue									8,905,000	8,265,300	9,463,600
Cost of revenue									8,588,100	7,940,600	9,191,500
Gross profit									316,900	324,700	272,100
Equity in earnings of joint ventures									116,200	76,700	86,200
General and administrative expenses									(8,700)
Gain (loss) on disposal activities									600	(42,600)
Income from operations									425,000	358,800	358,300
Other income (expense)									9,300	12,700	14,700
Interest (expense) income									(37,600)	(42,800)	(39,400)
Income (loss) before income tax (benefit) expense									396,700	328,700	333,600
Income tax (benefit) expense									65,100	27,800	61,000
Net income (loss)									331,600	300,900	272,600
Noncontrolling interests in income of consolidated subsidiaries, net of tax									(82,100)	(67,400)	(83,600)
Net income (loss) attributable to AECOM									249,500	233,500	189,000
Eliminations
Condensed Consolidating Statements of Operations
Revenue									(68,700)	(82,000)	(223,200)
Cost of revenue									(68,700)	(82,000)	(223,200)
Equity in earnings from subsidiaries									(656,500)	(681,000)	(520,200)
Income from operations									(656,500)	(681,000)	(520,200)
Other income (expense)									(36,500)	(40,000)	(35,600)
Interest (expense) income									36,500	40,000	35,600
Income (loss) before income tax (benefit) expense									(656,500)	(681,000)	(520,200)
Income tax (benefit) expense									31,700	37,300	45,300
Net income (loss)									(688,200)	(718,300)	(565,500)
Net income (loss) attributable to AECOM									$ (688,200)	$ (718,300)	$ (565,500)

Condensed Consolidating Financial Information - Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Consolidated Statements of Comprehensive Income (Loss)
Net income (loss)	$ 103,800	$ 136,100	$ 115,800	$ 65,800	$ 12,900	$ 84,400	$ 66,600	$ (400)	$ 421,476	$ 163,472	$ (71,233)
Other comprehensive income (loss), net of tax:
Net unrealized gain (loss) on derivatives, net of tax									4,605	5,987	(9,196)
Foreign currency translation adjustments									65,389	(65,224)	(285,520)
Pension adjustments, net of tax									87,061	(164,911)	12,953
Other comprehensive income (loss), net of tax									157,055	(224,148)	(281,763)
Comprehensive income (loss), net of tax									578,531	(60,676)	(352,996)
Noncontrolling interests in comprehensive income of consolidated subsidiaries, net of tax									(82,220)	(65,697)	(80,347)
Comprehensive income (loss) attributable to AECOM, net of tax									496,311	(126,373)	(433,343)
Reportable Legal Entities \| Parent
Consolidated Statements of Comprehensive Income (Loss)
Net income (loss)									339,300	96,200	(154,800)
Other comprehensive income (loss), net of tax:
Net unrealized gain (loss) on derivatives, net of tax									4,900	2,600	(6,100)
Pension adjustments, net of tax									7,100	(3,300)	1,800
Other comprehensive income (loss), net of tax									12,000	(700)	(4,300)
Comprehensive income (loss), net of tax									351,300	95,500	(159,100)
Comprehensive income (loss) attributable to AECOM, net of tax									351,300	95,500	(159,100)
Reportable Legal Entities \| Guarantor Subsidiaries
Consolidated Statements of Comprehensive Income (Loss)
Net income (loss)									438,800	484,700	376,500
Other comprehensive income (loss), net of tax:
Pension adjustments, net of tax									13,800	(14,900)	6,400
Other comprehensive income (loss), net of tax									13,800	(14,900)	6,400
Comprehensive income (loss), net of tax									452,600	469,800	382,900
Comprehensive income (loss) attributable to AECOM, net of tax									452,600	469,800	382,900
Reportable Legal Entities \| Non-Guarantor Subsidiaries
Consolidated Statements of Comprehensive Income (Loss)
Net income (loss)									331,600	300,900	272,600
Other comprehensive income (loss), net of tax:
Net unrealized gain (loss) on derivatives, net of tax									(300)	3,400	(3,100)
Foreign currency translation adjustments									65,400	(65,300)	(285,600)
Pension adjustments, net of tax									66,100	(146,700)	4,800
Other comprehensive income (loss), net of tax									131,200	(208,600)	(283,900)
Comprehensive income (loss), net of tax									462,800	92,300	(11,300)
Noncontrolling interests in comprehensive income of consolidated subsidiaries, net of tax									(82,200)	(65,700)	(80,300)
Comprehensive income (loss) attributable to AECOM, net of tax									380,600	26,600	(91,600)
Eliminations
Consolidated Statements of Comprehensive Income (Loss)
Net income (loss)									(688,200)	(718,300)	(565,500)
Other comprehensive income (loss), net of tax:
Comprehensive income (loss), net of tax									(688,200)	(718,300)	(565,500)
Comprehensive income (loss) attributable to AECOM, net of tax									$ (688,200)	$ (718,300)	$ (565,500)

Condensed Consolidating Financial Information - Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Condensed Consolidating Statements of Cash Flows
CASH FLOWS FROM OPERATING ACTIVITIES	$ 696,654	$ 814,155	$ 764,433
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments for business acquisitions, net of cash acquired	(103,075)	(5,534)	(3,293,284)
Proceeds from disposal of businesses, net of cash disposed	2,200	39,699	15,127
Net investment in unconsolidated joint ventures	(24,300)	(71,500)	(32,700)
Net purchases of investments	900
Net sales of investments		11,500
Sales (purchases) of investments			34,600
Payments for capital expenditures, net of disposals	(78,400)	(136,800)	(69,400)
Net cash used in investing activities	(202,711)	(162,615)	(3,345,728)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from borrowings under credit agreements	5,953,249	4,706,225	6,581,703
Repayments of borrowings under credit agreements	(7,071,602)	(5,199,961)	(5,158,254)
Issuance of unsecured senior notes	1,000,000		1,600,000
Redemption of unsecured senior notes	(179,208)
Prepayment penalty on unsecured senior notes			(55,639)
Cash paid for debt and equity issuance costs	(13,041)	(10,447)	(89,567)
Proceeds from issuance of common stock	30,093	28,192	25,561
Proceeds from exercise of stock options	4,878	9,946	11,073
Payments to repurchase common stock	(25,078)	(25,892)	(23,113)
Excess tax benefit from share-based payment			3,642
Net distributions to noncontrolling interests	(59,036)	(103,169)	(144,269)
Other financing activities	(26,745)	(42,873)	(31,373)
Net cash (used in) provided by financing activities	(386,490)	(637,979)	2,719,764
EFFECT OF EXCHANGE RATE CHANGES ON CASH	2,764	(5,309)	(28,764)
NET INCREASE IN CASH AND CASH EQUIVALENTS	110,217	8,252	109,705
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	692,145	683,893	574,188
CASH AND CASH EQUIVALENTS AT END OF YEAR	802,362	692,145	683,893
Reportable Legal Entities \| Parent
Condensed Consolidating Statements of Cash Flows
CASH FLOWS FROM OPERATING ACTIVITIES	(5,900)	(273,600)	(551,200)
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments for business acquisitions, net of cash acquired			(3,564,200)
Proceeds from disposal of businesses, net of cash disposed			9,500
Sales (purchases) of investments			37,300
Payments for capital expenditures, net of disposals	(21,700)	(82,000)	(51,900)
Net receipts from (investment in) intercompany notes	(4,600)	5,300	95,600
Other intercompany investing activities	139,000	791,200	1,085,800
Net cash used in investing activities	112,700	714,500	(2,387,900)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from borrowings under credit agreements	5,903,500	4,673,000	6,464,600
Repayments of borrowings under credit agreements	(6,956,300)	(5,124,100)	(5,031,900)
Issuance of unsecured senior notes	1,000,000		1,600,000
Prepayment penalty on unsecured senior notes			(55,600)
Cash paid for debt and equity issuance costs	(13,000)	(10,400)	(89,600)
Proceeds from issuance of common stock	30,100	28,200	25,600
Proceeds from exercise of stock options	4,900	9,900	11,100
Payments to repurchase common stock	(25,100)	(25,900)	(23,100)
Excess tax benefit from share-based payment			3,600
Other financing activities	(24,100)	7,900	2,300
Net borrowings (repayments) on intercompany notes	4,000	1,000
Net cash (used in) provided by financing activities	(76,000)	(440,400)	2,907,000
NET INCREASE IN CASH AND CASH EQUIVALENTS	30,800	500	(32,100)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	1,800	1,300	33,400
CASH AND CASH EQUIVALENTS AT END OF YEAR	32,600	1,800	1,300
Reportable Legal Entities \| Guarantor Subsidiaries
Condensed Consolidating Statements of Cash Flows
CASH FLOWS FROM OPERATING ACTIVITIES	691,200	623,700	816,900
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments for business acquisitions, net of cash acquired		(1,000)	109,200
Proceeds from disposal of businesses, net of cash disposed			5,600
Net investment in unconsolidated joint ventures	(2,600)	(3,900)	(4,000)
Payments for capital expenditures, net of disposals	(29,300)	(58,700)	(15,800)
Net receipts from (investment in) intercompany notes	102,800	176,100	128,600
Other intercompany investing activities	(221,000)	140,300	160,900
Net cash used in investing activities	(150,100)	252,800	384,500
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from borrowings under credit agreements	13,100	17,600	29,900
Repayments of borrowings under credit agreements	(51,100)	(22,800)	(31,200)
Redemption of unsecured senior notes	(179,200)
Other financing activities	(38,300)	(4,500)	(4,100)
Net borrowings (repayments) on intercompany notes	(16,300)	12,500
Other intercompany financing activities	(201,400)	(858,100)	(1,119,300)
Net cash (used in) provided by financing activities	(473,200)	(855,300)	(1,124,700)
NET INCREASE IN CASH AND CASH EQUIVALENTS	67,900	21,200	76,700
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	183,700	162,500	85,800
CASH AND CASH EQUIVALENTS AT END OF YEAR	251,600	183,700	162,500
Reportable Legal Entities \| Non-Guarantor Subsidiaries
Condensed Consolidating Statements of Cash Flows
CASH FLOWS FROM OPERATING ACTIVITIES	11,400	464,100	498,700
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments for business acquisitions, net of cash acquired	(103,100)	(4,500)	161,700
Proceeds from disposal of businesses, net of cash disposed	2,200	39,700
Net investment in unconsolidated joint ventures	(21,700)	(67,600)	(28,700)
Net purchases of investments	900
Net sales of investments		11,500
Sales (purchases) of investments			(2,700)
Payments for capital expenditures, net of disposals	(27,400)	3,900	(1,700)
Net receipts from (investment in) intercompany notes	12,200	(13,500)
Net cash used in investing activities	(136,900)	(30,500)	128,600
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from borrowings under credit agreements	36,600	15,600	87,200
Repayments of borrowings under credit agreements	(64,200)	(53,100)	(95,200)
Net distributions to noncontrolling interests	(59,000)	(103,200)	(144,300)
Other financing activities	35,600	(46,300)	(29,500)
Net borrowings (repayments) on intercompany notes	(98,100)	(181,400)	(224,200)
Other intercompany financing activities	283,400	(73,400)	(127,400)
Net cash (used in) provided by financing activities	134,300	(441,800)	(533,400)
EFFECT OF EXCHANGE RATE CHANGES ON CASH	2,800	(5,300)	(28,800)
NET INCREASE IN CASH AND CASH EQUIVALENTS	11,600	(13,500)	65,100
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	506,600	520,100	455,000
CASH AND CASH EQUIVALENTS AT END OF YEAR	518,200	506,600	520,100
Eliminations
CASH FLOWS FROM INVESTING ACTIVITIES:
Net receipts from (investment in) intercompany notes	(110,400)	(167,900)	(224,200)
Other intercompany investing activities	82,000	(931,500)	(1,246,700)
Net cash used in investing activities	(28,400)	(1,099,400)	(1,470,900)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net borrowings (repayments) on intercompany notes	110,400	167,900	224,200
Other intercompany financing activities	(82,000)	931,500	1,246,700
Net cash (used in) provided by financing activities	$ 28,400	$ 1,099,400	$ 1,470,900

Schedule II: Valuation and Qualifying Accounts (Details) - Allowance for Doubtful Accounts - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Changes in valuation and qualifying accounts
Balance at Beginning of Year	$ 60.4	$ 64.1	$ 72.1
Additions Charged to Cost of Revenue	13.1	16.4	26.9
Deductions	(20.7)	(20.5)	(31.2)
Other and Foreign Exchange Impact	(0.6)	0.4	(3.7)
Balance at the End of the Year	$ 52.2	$ 60.4	$ 64.1