Acquisitions and Divestitures - Acquisitions (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Dec. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Business Acquisition [Line Items]
Initial contributions from joint venture		$ 28	$ 0
Consolidated Entity | Adient Aerospace
Business Acquisition [Line Items]
Ownership interest (as percent)		50.01%
Americas | Consolidated Entity | Adient Aerospace
Business Acquisition [Line Items]
Initial contributions from joint venture	$ 28