Property and Equipment (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 790	$ 761
Less accumulated depreciation and amortization	(369)	(333)
Property and equipment, net	421	428
Land [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	103	106
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	213	224
Non-rental vehicles [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	67	64
Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	55	51
Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	160	141
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 192	$ 175