Other Current Assets - (Schedule of Other Current Assets) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Sales and use tax	$ 246	$ 108
Prepaid expenses	199	174
Other	154	123
Total other current assets	$ 599	$ 405