Segment Information - Income (Loss) Before Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Corporate-related costs	$ (2)	$ (28)	$ (3)	$ (42)
Becoming Adient costs	0	(19)	0	(38)
Restructuring and impairment costs	(113)	(315)	(144)	(315)
Purchase accounting amortization	(10)	(18)	(20)	(35)
Restructuring related charges	(14)	(12)	(23)	(23)
Stock based compensation	(2)	(12)	(8)	(22)
Depreciation	(72)	(99)	(137)	(193)
Earnings (loss) before interest and income taxes	(22)	(141)	32	(40)
Net financing charges	(40)	(37)	(75)	(70)
Other pension income	0	7	2	8
Income (loss) before income taxes	(62)	(171)	(41)	(102)
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Corporate-related costs	(25)	(23)	(48)	(50)
Americas | Operating segments
Segment Reporting Information [Line Items]
Adjusted EBITDA	34	98	77	133
EMEA | Operating segments
Segment Reporting Information [Line Items]
Adjusted EBITDA	59	130	61	212
Asia | Operating segments
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 123	$ 157	$ 277	$ 333