Basis of Presentation and Summary of Significant Accounting Policies - Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net income (loss) attributable to Adient	$ (167)	$ (17)
Denominator:
Shares outstanding (in shares)	93,700,000	93,500,000
Effect of dilutive securities (in shares)	0	0
Diluted shares (in shares)	93,700,000	93,500,000
Earnings per share, basic (in dollars per share)	$ (1.78)	$ (0.18)
Earnings per share, diluted (in dollars per share)	$ (1.78)	$ (0.18)