Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Total AECOM Stockholders’ Equity	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficits	Non- Controlling Interests
Beginning balance at Sep. 30, 2022	$ 2,605,379	$ 2,476,654	$ 1,389	$ 4,156,594	$ (979,675)	$ (701,654)	$ 128,725
Increase (Decrease) in Stockholders' Equity
Net income	100,141	55,332				55,332	44,809
Dividends declared	(100,872)	(100,872)				(100,872)
Other comprehensive loss	53,166	53,098			53,098		68
Issuance of stock	64,983	64,983	19	64,964
Repurchases of stock	(382,745)	(382,745)	(46)	(25,917)		(356,782)
Stock-based compensation	45,882	45,882		45,882
Contributions from noncontrolling interests	17,225						17,225
Distributions to noncontrolling interests	(19,448)						(19,448)
Ending balance at Sep. 30, 2023	2,383,711	2,212,332	1,362	4,241,523	(926,577)	(1,103,976)	171,379
Increase (Decrease) in Stockholders' Equity
Net income	460,255	402,266				402,266	57,989
Dividends declared	(120,454)	(120,454)				(120,454)
Other comprehensive loss	44,113	43,906			43,906		207
Issuance of stock	65,385	65,385	16	65,369
Repurchases of stock	(480,750)	(480,750)	(52)	(21,215)		(459,483)
Stock-based compensation	61,520	61,520		61,520
Contributions from noncontrolling interests	13,508						13,508
Distributions to noncontrolling interests	(56,878)						(56,878)
Ending balance at Sep. 30, 2024	2,370,410	2,184,205	1,326	4,347,197	(882,671)	(1,281,647)	186,205
Increase (Decrease) in Stockholders' Equity
Net income	636,187	561,774				561,774	74,413
Dividends declared	(139,303)	(139,303)				(139,303)
Other comprehensive loss	(10,387)	(10,356)			(10,356)		(31)
Issuance of stock	219,013	219,013	25	218,988
Repurchases of stock	(384,188)	(384,188)	(33)	(18,498)		(365,657)
Stock-based compensation	61,439	61,439		61,439
Effect of deconsolidation of a joint venture	(13,768)						(13,768)
Contributions from noncontrolling interests	2,450						2,450
Distributions to noncontrolling interests	(45,669)						(45,669)
Ending balance at Sep. 30, 2025	$ 2,696,184	$ 2,492,584	$ 1,318	$ 4,609,126	$ (893,027)	$ (1,224,833)	$ 203,600