Geographical Information - Revenue (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Revenue by Geographical Area
Revenue	$ 5,089		$ 3,711		$ 1,974
United States
Revenue by Geographical Area
Revenue	2,578		2,067		1,223
Rest of world
Revenue by Geographical Area
Revenue	$ 2,511	[1]	$ 1,644	[1]	$ 751	[1]

[1] (1)No individual country exceeded 10% of our total revenue for any period presented.