RELATED PARTY TRANSACTIONS (Details) - EBP 055 - USD ($) $ in Thousands |
12 Months Ended | |
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Dec. 31, 2025 |
Dec. 31, 2024 |
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| EBP, Related Party and Party-in-Interest Transactions [Line Items] | ||
| Total investments at fair value | $ 2,939,566 | $ 2,299,530 |
| Dividend income recorded | 5,100 | |
| Net depreciation in fair value of shares bought and sold, as well as held during the year | 48,300 | |
| Delinquent deposits of employee deferrals and loan repayments | $ 17,000 | $ 8,000 |
| AECOM common stock | ||
| EBP, Related Party and Party-in-Interest Transactions [Line Items] | ||
| Plan investments held (in shares) | 4,686,516 | 4,900,000 |
| Total investments at fair value | $ 446,500 | $ 521,700 |
| Investments acquired during the period | 59,800 | |
| AECOM common stock issued by the Company to the Plan | 26,000 | |
| Investments sold during the period | 91,700 | |
| In-kind distributions | $ 20,400 | |
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- Definition EBP, Investment Acquired, Excluding Plan Interest in Master Trust, Plan Sponsor's Non-Cash Issuance No definition available.
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- Definition EBP, Investment Sold, Excluding Plan Interest in Master Trust, In-Kind Distribution No definition available.
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- Definition Amount of increase (decrease) in net asset available for benefit from realized and unrealized gain (loss) on investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of increase in net asset available for benefit from dividend income on investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Cost of investment, excluding plan interest in master trust, acquired by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Fair value of investment, excluding plan interest in master trust, held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Includes, but is not limited to, derivative, investment measured at net asset value per share as practical expedient, and insurance contract not meeting fully-benefit responsive investment criteria. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Number of shares or units of investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount of selling price for investment, excluding plan interest in master trust, sold by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Amount of delinquent participant contribution transferred late to employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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