Organization and Summary of Significant Accounting Policies - Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Numerator:
Net income (loss) attributable to Adient	$ 18	$ 205	$ (120)
Denominator:
Shares outstanding (in shares)	89.5	94.5	94.8
Effect of dilutive securities (in shares)	0.6	0.9	0.0
Diluted shares (in shares)	90.1	95.4	94.8
Earnings per share:
Basic (in dollars per share)	$ 0.20	$ 2.17	$ (1.27)
Diluted (in dollars per share)	$ 0.20	$ 2.15	$ (1.27)