Business Segment Information - Schedule of Segment Assets (Details) - USD ($) $ in Millions	Dec. 31, 2021	Sep. 30, 2021
Segment Reporting Information [Line Items]
Total assets	$ 3,047	$ 2,938
Reportable Segments
Segment Reporting Information [Line Items]
Total assets	2,841	2,615
Reportable Segments | Commercial Truck
Segment Reporting Information [Line Items]
Total assets	2,174	1,961
Reportable Segments | Aftermarket & Industrial
Segment Reporting Information [Line Items]
Total assets	667	654
Corporate
Segment Reporting Information [Line Items]
Total assets	526	496
Segment Reconciling Items
Segment Reporting Information [Line Items]
Less: Accounts receivable sold under off-balance sheet factoring programs	$ (320)	$ (173)