Equity and Noncontrolling Interests - Changes in Equity (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2021	Jun. 30, 2020
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' equity, beginning balance	$ 1,842	$ 1,883	$ 2,189	$ 1,535	$ 2,189
Net income (loss)	(55)	(331)		199	(485)
Foreign currency translation adjustments	27	10		62	(65)
Realized and unrealized gains (losses) on derivatives	17	24		34	(23)
Dividends attributable to noncontrolling interests	(29)	(16)		(40)	(28)
Change in noncontrolling interest share			(18)	(3)	(18)
Share based compensation and other	8	2		20	6
Stockholders' equity, ending balance	1,807	1,572		1,807	1,572
Adjustments from adoption of a new standard
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' equity, beginning balance			(4)		(4)
Shareholders' Equity Attributable to Adient
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' equity, beginning balance	1,489	1,541	1,848	1,213	1,848
Net income (loss)	(71)	(325)		148	(511)
Foreign currency translation adjustments	24	8		53	(66)
Realized and unrealized gains (losses) on derivatives	17	24		34	(23)
Change in noncontrolling interest share				0
Share based compensation and other	8	2		19	6
Stockholders' equity, ending balance	1,467	1,250		1,467	1,250
Shareholders' Equity Attributable to Adient | Adjustments from adoption of a new standard
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' equity, beginning balance			(4)		(4)
Ordinary Shares
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' equity, beginning balance	0	0	0	0	0
Stockholders' equity, ending balance	0	0		0	0
Additional Paid-in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' equity, beginning balance	3,985	3,966	3,962	3,974	3,962
Share based compensation and other	8	2		19	6
Stockholders' equity, ending balance	3,993	3,968		3,993	3,968
Retained Earnings (Accumulated Deficit)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' equity, beginning balance	(1,877)	(1,735)	(1,545)	(2,096)	(1,545)
Net income (loss)	(71)	(325)		148	(511)
Stockholders' equity, ending balance	(1,948)	(2,060)		(1,948)	(2,060)
Retained Earnings (Accumulated Deficit) | Adjustments from adoption of a new standard
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' equity, beginning balance			(4)		(4)
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' equity, beginning balance	(619)	(690)	(569)	(665)	(569)
Foreign currency translation adjustments	24	8		53	(66)
Realized and unrealized gains (losses) on derivatives	17	24		34	(23)
Stockholders' equity, ending balance	(578)	(658)		(578)	(658)
Shareholders' Equity Attributable to Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' equity, beginning balance	353	342	$ 341	322	341
Net income (loss)	16	(6)		51	26
Foreign currency translation adjustments	3	2		9	1
Dividends attributable to noncontrolling interests	(29)	(16)		(40)	(28)
Change in noncontrolling interest share				(3)	(18)
Share based compensation and other	0			1
Stockholders' equity, ending balance	$ 340	$ 322		$ 340	$ 322