Property and Equipment (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 1,227	$ 1,004
Less accumulated depreciation and amortization	(613)	(537)
Property and equipment, net	614	467
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	103	102
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	277	238
Non-rental vehicles
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	200	112
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	135	103
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	240	204
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 272	$ 245