Components Of Vehicle Depreciation And Lease Charges (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Vehicle Depreciation and Lease Charges, Net [Line Items]
Depreciation expense	$ 1,947	$ 1,877	$ 1,837
Lease charges	222	180	156
(Gain) loss on sale of vehicles, net	52	(10)	(60)
Vehicle depreciation and lease charges, net	2,221	2,047	1,933
Accounts Payable, Other, Current	346	321	269
Receivables due from former subsidiaries	$ 545	$ 520	$ 433