Goodwill (Details) $ in Millions		9 Months Ended
		Jun. 30, 2017 USD ($) segment	Sep. 30, 2016 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Number of operating segments | segment		2
Number of reportable segments | segment		2
Goodwill [Line Items]
Goodwill gross			$ 405
Accumulated impairment losses, Beginning balance			(15)
Goodwill [Roll Forward]
Goodwill net, Beginning balance	[1]	$ 390
Foreign currency translation		1
Goodwill net, Ending balance	[1]	391
Commercial Truck & Industrial
Goodwill [Line Items]
Goodwill gross			245
Accumulated impairment losses, Beginning balance			(15)
Goodwill [Roll Forward]
Goodwill net, Beginning balance		230
Foreign currency translation		0
Goodwill net, Ending balance		230
Aftermarket & Trailer
Goodwill [Line Items]
Goodwill gross			160
Accumulated impairment losses, Beginning balance			$ 0
Goodwill [Roll Forward]
Goodwill net, Beginning balance		160
Foreign currency translation		1
Goodwill net, Ending balance		$ 161

[1] As of June 30, 2017, Assets and Liabilities held for sale were: (i) $1 million Cash and cash equivalents; (ii) $11 million Receivables, trade and other, net; (iii) $2 million Inventories; (iv) $3 million Net property; (v) $1 million Goodwill; (vi) $10 million Accounts and notes payable; and (vii) $2 million Noncontrolling interests. As of September 30, 2016, Assets and Liabilities held for sale were: (i) $1 million Cash and cash equivalents; (ii) $8 million Receivables, trade and other, net; (iii) $1 million Inventories; (iv) $5 million Net property; (v) $5 million Accounts and notes payable; and (vi) $3 million Noncontrolling interests.