Components of Company's Vehicles (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure Components Of Companys Vehicles [Abstract]
Rental vehicles	$ 11,652	$ 10,937
Less: Accumulated depreciation	(1,652)	(1,454)
Rental Vehicles Net, Total	10,000	9,483
Vehicles held for sale	626	981
Vehicles, net	$ 10,626	$ 10,464