Business Segment Information - Schedule of Segment Assets (Details) - USD ($) $ in Millions	Dec. 31, 2018	Sep. 30, 2018
Segment Reporting Information [Line Items]
Total assets	$ 2,733	$ 2,726
Operating Segments
Segment Reporting Information [Line Items]
Total assets	2,402	2,353
Operating Segments | Commercial Truck & Trailer
Segment Reporting Information [Line Items]
Total assets	1,901	1,858
Operating Segments | Aftermarket & Industrial
Segment Reporting Information [Line Items]
Total assets	501	495
Corporate
Segment Reporting Information [Line Items]
Total assets	625	633
Segment Reconciling Items
Segment Reporting Information [Line Items]
Less: Accounts receivable sold under off-balance sheet factoring programs	$ (294)	$ (260)