Segment Information - Other Reconciling Items (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Net Sales			$ 13,680	$ 12,670	$ 16,526
Equity Income			1,484	22	275
Total assets			10,778	10,261	10,342
Depreciation			285	295	278
Amortization			45	37	40
Capital Expenditures			260	326	468
Purchase accounting amortization			5	3	4
Yanfeng
Segment Reporting Information [Line Items]
Equity method investment, realized gain (loss) on disposal			1,181
Gain on completion of transaction				12
SJA
Segment Reporting Information [Line Items]
Equity method investment, realized gain (loss) on disposal	$ 33	$ 33	33
Yanfeng Adient Seating Co., Ltd. (YFAS)
Segment Reporting Information [Line Items]
Gain on completion of transaction			5
YFAI
Segment Reporting Information [Line Items]
Equity Income					40
Purchase accounting amortization			5	3	4
Restructuring charges			1	8	5
(Gain) on sale of / impairment of nonconsolidated partially owned affiliates				231
Impact of tax reform				1	2
Reportable Segments | Americas
Segment Reporting Information [Line Items]
Net Sales			6,164	5,889	7,785
Equity Income			(1)	1	3
Total assets			2,888	3,019	3,237
Depreciation			121	128	109
Amortization			13	13	14
Capital Expenditures			131	138	190
Reportable Segments | EMEA
Segment Reporting Information [Line Items]
Net Sales			5,564	5,148	6,675
Equity Income			7	8	13
Total assets			2,473	2,658	2,716
Depreciation			132	129	126
Amortization			14	8	5
Capital Expenditures			104	164	237
Reportable Segments | Asia
Segment Reporting Information [Line Items]
Net Sales			2,123	1,822	2,337
Equity Income			265	256	270
Total assets			3,187	2,868	3,416
Depreciation			32	38	43
Amortization			18	16	18
Capital Expenditures			25	24	41
Reconciling items
Segment Reporting Information [Line Items]
Net Sales			(171)	(189)	(271)
Equity Income			1,213	(243)	(11)
Total assets			2,230	1,716	973
Depreciation			0	0	0
Amortization			0	0	3
Capital Expenditures			$ 0	$ 0	$ 0