Basis of Presentation and Summary of Significant Accounting Policies - Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Numerator:
Net income (loss) attributable to Adient	$ (491)	$ (1,685)	$ 877
Denominator:
Shares outstanding (in shares)	93,600,000	93,300,000	93,500,000
Effect of dilutive securities (in shares)	0	0	400,000
Diluted shares (in shares)	93,600,000	93,300,000	93,900,000
Earnings per share:
Basic earnings per share (in dollars per share)	$ (5.25)	$ (18.06)	$ 9.38
Diluted earnings per share (in dollars per share)	$ (5.25)	$ (18.06)	$ 9.34