Property and Equipment, Net - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Property Plant And Equipment [Abstract]
Depreciation expenses	$ 29	$ 36	$ 61	$ 72
Net Capital lease assets	89		89		94
Property and equipment additions			$ 51	$ 37