Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 179,204	$ 108,594
Other comprehensive (loss) income, net of tax:
Net unrealized gain (loss) on derivatives, net of tax	9,139	(14,212)
Foreign currency translation adjustments	(105,961)	60,164
Pension adjustments, net of tax	14,311	(8,998)
Other comprehensive (loss) income, net of tax	(82,511)	36,954
Comprehensive income, net of tax	96,693	145,548
Noncontrolling interests in comprehensive income of consolidated subsidiaries, net of tax	(11,774)	(14,321)
Comprehensive income attributable to AECOM, net of tax	$ 84,919	$ 131,227