Consolidated Statements of Stockholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Total AECOM Stockholders' Equity	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Retained Earnings	Non-Controlling Interests	Comprehensive Income	Convertible Preferred Stock Preferred Stock
BALANCE at Sep. 30, 2009	$ 1,754,405	$ 1,729,718	$ 1,109	$ 1,458,326	$ (146,575)	$ 414,345	$ 24,687		$ 2,513
Comprehensive income (loss), net of tax:
Net (loss) income	249,344	236,887				236,887	12,457	249,344
Foreign currency translation adjustments	32,142	32,142			32,142			32,142
Defined benefit minimum pension liability adjustment, net of tax	(34,219)	(34,219)			(34,219)			(34,219)
Gain (Loss) on cash flow hedge valuations	1,131	1,131			1,131			1,131
Total comprehensive income (loss), net of tax	248,398	235,941					12,457	248,398
Issuance of stock	79,302	79,302	32	79,270
Repurchases of stock	(17,171)	(17,171)	(7)	(14,755)					(2,409)
Preferred stock dividend						(127)			127
Proceeds from exercise of options	10,310	10,310	10	10,300
Tax benefit from exercise of stock options	17,306	17,306		17,306
Stock based compensation	34,606	34,606	9	34,597
Other transactions with noncontrolling interests	4,801						4,801
Contributions from noncontrolling interests	17,488						17,488
Distributions to noncontrolling interests	(10,976)						(10,976)
BALANCE at Sep. 30, 2010	2,138,469	2,090,012	1,153	1,585,044	(147,521)	651,105	48,457		231
Comprehensive income (loss), net of tax:
Net (loss) income	284,090	275,800				275,800	8,290	284,090
Foreign currency translation adjustments	(45,609)	(45,609)			(45,609)			(45,609)
Defined benefit minimum pension liability adjustment, net of tax	5,556	5,556			5,556			5,556
Total comprehensive income (loss), net of tax	244,037	235,747					8,290	244,037
Issuance of stock	88,531	88,531	36	88,495
Repurchases of stock	(167,044)	(167,044)	(70)	(66,784)		(99,957)			(233)
Preferred stock dividend						(2)			2
Proceeds from exercise of options	6,280	6,280	5	6,275
Tax benefit from exercise of stock options	61,248	61,248		61,248
Stock based compensation	24,937	24,937	8	24,929
Other transactions with noncontrolling interests	(20)						(20)
Contributions from noncontrolling interests	1,700						1,700
Distributions to noncontrolling interests	(3,001)						(3,001)
BALANCE at Sep. 30, 2011	2,395,137	2,339,711	1,132	1,699,207	(187,574)	826,946	55,426
Comprehensive income (loss), net of tax:
Net (loss) income	(56,933)	(58,567)				(58,567)	1,634	(56,933)
Foreign currency translation adjustments	53,895	53,895			53,895			53,895
Defined benefit minimum pension liability adjustment, net of tax	(41,778)	(41,778)			(41,778)			(41,778)
Gain (Loss) on cash flow hedge valuations	(3,716)	(3,716)			(3,716)			(3,716)
Total comprehensive income (loss), net of tax	(48,532)	(50,166)					1,634	(48,532)
Issuance of stock	18,631	18,631	9	18,622
Repurchases of stock	(169,454)	(169,454)	(83)	(7,081)		(162,290)
Proceeds from exercise of options	4,541	4,541	4	4,537
Tax benefit from exercise of stock options	(350)	(350)		(350)
Stock based compensation	26,551	26,551	8	26,543
Other transactions with noncontrolling interests	(753)						(753)
Distributions to noncontrolling interests	(1,283)						(1,283)
BALANCE at Sep. 30, 2012	$ 2,224,488	$ 2,169,464	$ 1,070	$ 1,741,478	$ (179,173)	$ 606,089	$ 55,024