Intangible Assets (Schedule Of Intangible Assets) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Finite And Indefinite Lived Intangible Assets [Line Items]
Amortized Intangible Assets, Gross Carrying Amount	$ 416		$ 345
Amortized Intangible Assets, Accumulated Amortization	64		59
Amortized Intangible Assets, Net Carrying Amount	352		286
Unamortized Intangible Assets, Goodwill, Gross Carrying Amount	646		375
License Agreements [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Amortized Intangible Assets, Gross Carrying Amount	251		257
Amortized Intangible Assets, Accumulated Amortization	42		39
Amortized Intangible Assets, Net Carrying Amount	209		218
Customer Relationships [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Amortized Intangible Assets, Gross Carrying Amount	163		86
Amortized Intangible Assets, Accumulated Amortization	21		19
Amortized Intangible Assets, Net Carrying Amount	142		67
Other Intangible Assets [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Amortized Intangible Assets, Gross Carrying Amount	2		2
Amortized Intangible Assets, Accumulated Amortization	1		1
Amortized Intangible Assets, Net Carrying Amount	1		1
Goodwill [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Unamortized Intangible Assets, Goodwill, Gross Carrying Amount	646	[1]	375	[1]
Trademarks [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Unamortized Intangible Assets, Trademarks, Gross Carrying Amount	$ 558	[1]	$ 445	[1]

[1] The increases in carrying amounts primarily relate to the acquisition of Zipcar.