Stock-Based Compensation - Stock Options (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2019 USD ($) $ / shares shares
Weighted Average Option Price
Outstanding options, weighted average exercise price at beginning period (in dollars per share) | $ / shares	$ 34.51
Options exercised, weighted average exercise price (in dollars per share) | $ / shares	25.76
Options forfeited, expired or converted, weighted average exercise price (in dollars per share) | $ / shares	41.89
Outstanding options, weighted average exercise price at ending period (in dollars per share) | $ / shares	38.25
Options exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 38.25
Shares Subject to Option
Options outstanding at beginning period (in shares) | shares	1,087,981
Options exercised (in shares) | shares	(368,128)
Options forfeited, expired or converted (in shares) | shares	(128,223)
Options outstanding at ending period (in shares) | shares	591,630
Options exercisable (in shares) | shares	591,630
Weighted Average Remaining Contractual Life
Options outstanding, weighted average remaining contractual life	4 years
Options exercisable, weighted average remaining contractual life	4 years
Aggregate Intrinsic Value
Options outstanding, aggregate intrinsic value | $	$ 4
Options exercisable, aggregate intrinsic value | $	$ 4
Former Parent Plan
Weighted Average Option Price
Outstanding options, weighted average exercise price at ending period (in dollars per share) | $ / shares	$ 38.52
Options exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 38.52
Shares Subject to Option
Options outstanding at ending period (in shares) | shares	505,849
Options exercisable (in shares) | shares	505,849
Weighted Average Remaining Contractual Life
Options outstanding, weighted average remaining contractual life	4 years 2 months 12 days
Options exercisable, weighted average remaining contractual life	4 years 2 months 12 days
Aggregate Intrinsic Value
Options outstanding, aggregate intrinsic value | $	$ 4
Options exercisable, aggregate intrinsic value | $	$ 4
Adient Plan
Weighted Average Option Price
Outstanding options, weighted average exercise price at ending period (in dollars per share) | $ / shares	$ 37.36
Options exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 37.36
Shares Subject to Option
Options outstanding at ending period (in shares) | shares	85,781
Options exercisable (in shares) | shares	85,781
Weighted Average Remaining Contractual Life
Options outstanding, weighted average remaining contractual life	3 years 3 months 18 days
Options exercisable, weighted average remaining contractual life	3 years 3 months 18 days
Aggregate Intrinsic Value
Options outstanding, aggregate intrinsic value | $	$ 0
Options exercisable, aggregate intrinsic value | $	$ 0
Former Parent and Adient Plan
Weighted Average Option Price
Outstanding options, weighted average exercise price at ending period (in dollars per share) | $ / shares	$ 38.35
Options exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 38.35
Shares Subject to Option
Options outstanding at ending period (in shares) | shares	591,630
Options exercisable (in shares) | shares	591,630
Weighted Average Remaining Contractual Life
Options outstanding, weighted average remaining contractual life	4 years
Options exercisable, weighted average remaining contractual life	4 years
Aggregate Intrinsic Value
Options outstanding, aggregate intrinsic value | $	$ 4
Options exercisable, aggregate intrinsic value | $	$ 4