Stock-Based Compensation - Stock Appreciation Rights (Details) - Stock Appreciation Rights (SARs) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2019 USD ($) $ / shares shares
Weighted Average SAR Price
Shares outstanding, weighted average exercise price at beginning period (in dollars per share) | $ / shares	$ 29.12
Shares exercised, weighted average exercise price (in dollars per share) | $ / shares	24.08
Shares forfeited or expired, weighted average exercise price (in dollars per share) | $ / shares	33.19
Shares outstanding, weighted average exercise price at ending period (in dollars per share) | $ / shares	30.24
Shares exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 30.24
Shares Subject to SAR
Shares outstanding at beginning of period (In shares) | shares	291,464
Shares exercised (in shares) | shares	(80,732)
Shares forfeited or expired (In shares) | shares	(19,074)
Shares outstanding at ending of period (In shares) | shares	391,270
Shares exercisable (in shares) | shares	291,464
Weighted Average Remaining Contractual Life
Shares outstanding, weighted average remaining contractual life	2 years 9 months 18 days
Shares exercisable, weighted average remaining contractual life	2 years 9 months 18 days
Aggregate Intrinsic Value
Shares outstanding, aggregate intrinsic value | $	$ 4
Shares exercisable, aggregate intrinsic value | $	$ 4
Former Parent Plan
Weighted Average SAR Price
Shares outstanding, weighted average exercise price at ending period (in dollars per share) | $ / shares	$ 29.96
Shares exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 29.96
Shares Subject to SAR
Shares outstanding at beginning of period (In shares) | shares	270,183
Shares exercisable (in shares) | shares	270,183
Weighted Average Remaining Contractual Life
Shares outstanding, weighted average remaining contractual life	2 years 9 months 18 days
Shares exercisable, weighted average remaining contractual life	2 years 9 months 18 days
Aggregate Intrinsic Value
Shares outstanding, aggregate intrinsic value | $	$ 4
Shares exercisable, aggregate intrinsic value | $	$ 4
Adient Plan
Weighted Average SAR Price
Shares outstanding, weighted average exercise price at ending period (in dollars per share) | $ / shares	$ 33.87
Shares exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 33.87
Shares Subject to SAR
Shares outstanding at beginning of period (In shares) | shares	21,281
Shares exercisable (in shares) | shares	21,281
Weighted Average Remaining Contractual Life
Shares outstanding, weighted average remaining contractual life	2 years 9 months 18 days
Shares exercisable, weighted average remaining contractual life	2 years 9 months 18 days
Aggregate Intrinsic Value
Shares outstanding, aggregate intrinsic value | $	$ 0
Shares exercisable, aggregate intrinsic value | $	$ 0