Equity and Noncontrolling Interests Equity and Noncontrolling Interests - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2016
Equity, Class of Treasury Stock [Line Items]
Deferred tax asset from stock options exercised and restricted stock vestings	$ 179
Stock repurchase program, authorized amount	1,000
Treasury Stock, Value, Acquired, Cost Method	150	$ 0
Stock Repurchase Program, Remaining Authorized Repurchase Amount	1,200
Post Merger Stock Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount			$ 1,000
Parent
Equity, Class of Treasury Stock [Line Items]
Stockholder's equity, spin-off of Adient	0	(4,020)
Treasury Stock, Value, Acquired, Cost Method	$ 150	$ 0