INVESTMENT IN AECOM DC RETIREMENT PLANS STABLE VALUE MASTER TRUST (Details) - EBP 055 - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
EBP, Master Trust [Line Items]
Investments at fair value	$ 7,291,530	$ 6,704,959
Stable Value Master Trust
EBP, Master Trust [Line Items]
Plan's interest in Master Trust (percent)	100.00%
Master Trust \| Stable Value Master Trust
EBP, Master Trust [Line Items]
Investments at fair value	$ 313,784	323,734
Unfunded Commitment	0	0
Master Trust \| Collective investment trusts (measured at NAV) \| Investments measured at NAV \| Stable Value Master Trust
EBP, Master Trust [Line Items]
Investments at fair value	313,784	323,734
Plan interest in Master Trust \| Stable Value Master Trust
EBP, Master Trust [Line Items]
Investments at fair value	313,784	323,734
Unfunded Commitment	0	0
Plan interest in Master Trust \| Collective investment trusts (measured at NAV) \| Investments measured at NAV \| Stable Value Master Trust
EBP, Master Trust [Line Items]
Investments at fair value	$ 313,784	$ 323,734

Amount of unfunded commitment for investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), that is fair value measured at net asset value (NAV) per share as practical expedient.

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