Derivative instruments (Details 3) (Foreign currency contracts [Member], Interest and other income, net [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Foreign currency contracts [Member] | Interest and other income, net [Member]
Location in the Condensed Consolidated Statements of Income and the amount of gain (loss) recognized in earnings for our derivative instruments not designated as hedging instruments
Derivatives not designated as hedging instruments	$ 19	$ (1)	$ 32