Equity and Noncontrolling Interests - Schedule of Stockholders Equity (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' equity, beginning balance	$ 1,949	$ 2,402	$ 2,443	$ 2,546
Net income (loss)	50	(2)	(256)	(26)
Foreign currency translation adjustments	123	(47)	(12)	(9)
Realized and unrealized losses on derivatives	22	(23)	31	(20)
Dividends attributable to noncontrolling interests	(27)	(39)	(42)	(57)
Purchase of noncontrolling interest			(28)
Repurchases of common stock	(50)	(75)	(75)	(225)
Share based compensation and other	7	6	13	13
Stockholders' equity, ending balance	2,074	2,222	2,074	2,222
Shareholders' Equity Attributable to Adient
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' equity, beginning balance	1,652	2,075	2,134	2,228
Net income (loss)	36	(11)	(299)	(61)
Foreign currency translation adjustments	118	(44)	(10)	(7)
Realized and unrealized losses on derivatives	22	(23)	31	(20)
Purchase of noncontrolling interest			(9)
Repurchases of common stock	(50)	(75)	(75)	(225)
Share based compensation and other	7	5	13	12
Stockholders' equity, ending balance	1,785	1,927	1,785	1,927
Ordinary Shares
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' equity, beginning balance	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	3,686	3,830	3,712	3,973
Purchase of noncontrolling interest			(7)
Repurchases of common stock	(50)	(75)	(75)	(225)
Share based compensation and other	7	5	13	12
Stockholders' equity, ending balance	3,643	3,760	3,643	3,760
Retained Earnings (Accumulated Deficit)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' equity, beginning balance	(1,220)	(953)	(885)	(903)
Net income (loss)	36	(11)	(299)	(61)
Stockholders' equity, ending balance	(1,184)	(964)	(1,184)	(964)
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' equity, beginning balance	(814)	(802)	(693)	(842)
Foreign currency translation adjustments	118	(44)	(10)	(7)
Realized and unrealized losses on derivatives	22	(23)	31	(20)
Purchase of noncontrolling interest			(2)
Stockholders' equity, ending balance	(674)	(869)	(674)	(869)
Shareholders' Equity Attributable to Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' equity, beginning balance	297	327	309	318
Net income (loss)	14	9	43	35
Foreign currency translation adjustments	5	(3)	(2)	(2)
Dividends attributable to noncontrolling interests	(27)	(39)	(42)	(57)
Purchase of noncontrolling interest			(19)
Share based compensation and other		1		1
Stockholders' equity, ending balance	$ 289	$ 295	$ 289	$ 295