Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Income Statement [Abstract]
Revenue	$ 4,178,440	$ 4,151,251	$ 11,964,205	$ 11,995,004
Cost of revenue	3,851,490	3,866,207	11,078,090	11,204,816
Gross profit	326,950	285,044	886,115	790,188
Equity in earnings (losses) of joint ventures	5,290	7,647	21,707	(1,835)
General and administrative expenses	(38,163)	(36,209)	(118,676)	(116,619)
Restructuring costs	0	(29,025)	0	(80,670)
Income from operations	294,077	227,457	789,146	591,064
Other income (loss)	823	963	(1,001)	6,154
Interest income	14,063	15,817	45,157	43,341
Interest expense	(40,198)	(51,370)	(125,437)	(140,350)
Income from continuing operations before taxes	268,765	192,867	707,865	500,209
Income tax expense for continuing operations	65,148	46,035	145,618	118,078
Net income from continuing operations	203,617	146,832	562,247	382,131
Net (loss) income from discontinued operations	(43,880)	5,677	(63,766)	(104,998)
Net income	159,737	152,509	498,481	277,133
Net income attributable to noncontrolling interests from continuing operations	(28,771)	(17,355)	(55,953)	(44,585)
Net income attributable to noncontrolling interests from discontinued operations	0	(881)	(1,126)	(2,830)
Net income attributable to noncontrolling interests	(28,771)	(18,236)	(57,079)	(47,415)
Net income attributable to AECOM from continuing operations	174,846	129,477	506,294	337,546
Net (loss) income attributable to AECOM from discontinued operations	(43,880)	4,796	(64,892)	(107,828)
Net income attributable to AECOM	$ 130,966	$ 134,273	$ 441,402	$ 229,718
Net income (loss) attributable to AECOM per share:
Basic continuing operations per share (in dollar per share)	$ 1.32	$ 0.95	$ 3.82	$ 2.48
Basic discontinued operations per share (in dollar per share)	(0.33)	0.04	(0.49)	(0.79)
Basic earnings per share (in dollar per share)	0.99	0.99	3.33	1.69
Diluted continuing operations per share (in dollar per share)	1.31	0.95	3.80	2.47
Diluted discontinued operations per share (in dollar per share)	(0.33)	0.03	(0.49)	(0.79)
Diluted earnings per share (in dollar per share)	$ 0.98	$ 0.98	$ 3.31	$ 1.68
Weighted average shares outstanding:
Basic (in shares)	132,301	136,025	132,411	135,976
Diluted (in shares)	133,078	136,790	133,281	136,868