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, 2025	Sep. 30, 2024	Sep. 30, 2023
Numerator:
Net income (loss) attributable to Adient	$ (281)	$ 18	$ 205
Denominator:
Shares outstanding (in shares)	83.0	89.5	94.5
Effect of dilutive securities (in shares)	0.0	0.6	0.9
Diluted shares (in shares)	83.0	90.1	95.4
Earnings (Loss) per share:
Basic (in dollars per share)	$ (3.39)	$ 0.20	$ 2.17
Diluted (in dollars per share)	$ (3.39)	$ 0.20	$ 2.15