Represents the consolidated interest coverage ratio.

No definition available.

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Namespace Prefix:	acm_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Face (par) amount of the original debt instrument that was repurchased.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentRepurchasedFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentsAbstract
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Indebtedness divided by net capital.

+ References

No definition available.

+ Details

Name:	us-gaap_RatioOfIndebtednessToNetCapital1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Details

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Namespace Prefix:
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- Details

Name:	us-gaap_VariableRateAxis=us-gaap_BaseRateMember
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Data Type:	na
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- Details

Name:	us-gaap_VariableRateAxis=us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=acm_TermLoanFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=acm_CreditAgreementMember
Namespace Prefix:
Data Type:	na
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- Details

Name:	srt_RangeAxis=srt_MinimumMember
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- Details

Name:	srt_RangeAxis=srt_MaximumMember
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- Details

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- Details

Name:	us-gaap_DebtInstrumentAxis=acm_SeniorNotes2024Member
Namespace Prefix:
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Debt - Credit Agreement (Details)	May 23, 2023	Feb. 08, 2021 USD ($)	Dec. 31, 2023 USD ($)	Sep. 30, 2023 USD ($)	Jun. 25, 2021 USD ($)	Apr. 13, 2021 USD ($)
2014 Credit Agreement \| Base Rate
Debt agreements
Interest rate, basis spread (as a percent)	0.75%
2014 Credit Agreement \| SOFR
Debt agreements
Interest rate, basis spread (as a percent)	1.75%
2014 Credit Agreement \| Term loan A
Debt agreements
Maximum borrowing capacity					$ 215,000,000
Credit Agreement
Debt agreements
Consolidated leverage ratio			2.00
Credit Agreement \| Base Rate
Debt agreements
Interest rate, basis spread (as a percent)		0.225%
Credit Agreement \| SOFR
Debt agreements
Interest rate, basis spread (as a percent)		1.225%
Credit Agreement \| Minimum
Debt agreements
Consolidated interest coverage ratio		3.00
Credit Agreement \| Maximum
Debt agreements
Consolidated leverage ratio		4.00
Credit Agreement \| Term loan A
Debt agreements
Maximum borrowing capacity		$ 246,968,737.50
Credit Agreement \| Term B facility
Debt agreements
Maximum borrowing capacity						$ 700,000,000
Credit Agreement \| Revolving credit facility
Debt agreements
Maximum borrowing capacity		$ 1,150,000,000
Current borrowing capacity			$ 1,145,600,000	$ 1,145,600,000
Outstanding letters of credit			$ 4,400,000	$ 4,400,000
2024 Senior Notes
Debt agreements
Cash tender offer to purchase						$ 700,000,000
Interest rate (as a percent)					5.875%	5.875%