Business Segment Information - Schedule of Segment Assets (Details) - USD ($) $ in Millions	Jun. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Total assets	$ 2,728	$ 2,726
Operating Segments
Segment Reporting Information [Line Items]
Total assets	2,455	2,353
Operating Segments | Commercial Truck
Segment Reporting Information [Line Items]
Total assets	1,846	1,764
Operating Segments | Aftermarket, Industrial and Trailer
Segment Reporting Information [Line Items]
Total assets	609	589
Corporate
Segment Reporting Information [Line Items]
Total assets	567	633
Segment Reconciling Items
Segment Reporting Information [Line Items]
Less: Accounts receivable sold under off-balance sheet factoring programs	$ (294)	$ (260)