Acquisitions and Divestitures (Details) ¥ in Millions, $ in Millions	1 Months Ended			3 Months Ended	12 Months Ended
	Nov. 30, 2023 USD ($)	Apr. 30, 2023 USD ($)	Apr. 30, 2023 CNY (¥)	Dec. 31, 2024 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2023 CNY (¥)	Sep. 30, 2022 USD ($)	Sep. 30, 2022 CNY (¥)	Sep. 30, 2024 USD ($)	Nov. 30, 2023 CNY (¥)	Oct. 31, 2023
Business Combination [Line Items]
Goodwill					$ 1,807	$ 2,094				$ 2,164
Asia
Business Combination [Line Items]
Goodwill					1,200	1,168				$ 1,217
Disposed of By Sale | Adient (Langfang) Seating Co., Ltd
Business Combination [Line Items]
Subsidiary, ownership percentage disposed (as percent)	51.00%										51.00%
Consideration for disposal group	$ 6										¥ 44
Deconsolidated cash	9
Loss on disposal	8
Disposed of By Sale | Adient (Langfang) Seating Co., Ltd | Asia
Business Combination [Line Items]
Disposal group, including discontinued operation, goodwill	$ 5
Assets Held for Sale | Adient (Langfang) Seating Co., Ltd
Business Combination [Line Items]
Subsidiary, ownership percentage disposed (as percent)												100.00%
Setex, Inc.
Business Combination [Line Items]
Proceeds from sale of equity method investments				$ 27
Realized gain on disposal				4	$ 4
Technotrim, Inc.
Business Combination [Line Items]
Net purchase consideration				$ 28
YFAT
Business Combination [Line Items]
Business combination, deposit to acquire interest in joint venture						$ 11	¥ 75	$ 12	¥ 75
Business combination, deposit, percent of total consideration (as percent)								50.00%	50.00%
Goodwill		$ 13
Cash acquired		5
YFAT | KEIPER Seating Mechanisms Co., Ltd
Business Combination [Line Items]
Net purchase consideration		$ 23	¥ 150