Debt and Financing Arrangements - Outstanding Obligations Confirmed Under Supplier Finance Program (Details) $ in Millions	12 Months Ended
Sep. 30, 2025 USD ($)
Supplier Finance Program, Obligation [Roll Forward]
Balance at beginning of period	$ 76
Invoices confirmed	122
Confirmed invoices paid	(96)
Currency translations	3
Balance at end of period	$ 105

Supplier Finance Program, Obligation, Foreign Currency Translation Gain (Loss)

No definition available.

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Namespace Prefix:	adnt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of obligation for supplier finance program, classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 50
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479468/405-50-50-3

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 50
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479468/405-50-50-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 50
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479468/405-50-50-4

+ Details

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

- Definition

Amount of decrease in obligation for supplier finance program from settlement.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 405
-SubTopic 50
-Name Accounting Standards Codification
-Section 55
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477128/405-50-55-5

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 50
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479468/405-50-50-3

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of increase in obligation for supplier finance program.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 405
-SubTopic 50
-Name Accounting Standards Codification
-Section 55
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477128/405-50-55-5

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 50
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479468/405-50-50-3

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration