Net Property (Details) - USD ($) $ in Millions	Mar. 31, 2021	Sep. 30, 2020
Property, Plant and Equipment [Line Items]
Property at cost	$ 1,512	$ 1,476
Less: accumulated depreciation	(1,010)	(961)
Net property	502	515
Land and land improvements
Property, Plant and Equipment [Line Items]
Property at cost	33	32
Buildings
Property, Plant and Equipment [Line Items]
Property at cost	238	228
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property at cost	1,045	1,002
Company-owned tooling
Property, Plant and Equipment [Line Items]
Property at cost	158	151
Construction in progress
Property, Plant and Equipment [Line Items]
Property at cost	$ 38	$ 63