Business Segment Information - Schedule of Segment Assets (Details) - USD ($) $ in Millions	Mar. 31, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Total assets	$ 3,322	$ 2,938
Reportable Segments
Segment Reporting Information [Line Items]
Total assets	3,050	2,615
Reportable Segments | Commercial Truck
Segment Reporting Information [Line Items]
Total assets	2,338	1,961
Reportable Segments | Aftermarket & Industrial
Segment Reporting Information [Line Items]
Total assets	712	654
Corporate
Segment Reporting Information [Line Items]
Total assets	522	496
Segment Reconciling Items
Segment Reporting Information [Line Items]
Less: Accounts receivable sold under off-balance sheet factoring programs	(250)	(173)
Accounts receivable sold under off-balance sheet factoring programs	$ 250	$ 173