Derivative instruments (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Location in the Consolidated Statements of Income and the effective portion of gain (loss) reclassified from Accumulated Other Comprehensive Income into earnings for our derivative instruments designated as cash flow hedges
Total	$ (144)	$ 24
Foreign currency contracts [Member]
Location in the Consolidated Statements of Income and the effective portion of gain (loss) reclassified from Accumulated Other Comprehensive Income into earnings for our derivative instruments designated as cash flow hedges
The amount of gain (loss) recognized in product sales	(4)	11
Cross currency swap contracts [Member]
Location in the Consolidated Statements of Income and the effective portion of gain (loss) reclassified from Accumulated Other Comprehensive Income into earnings for our derivative instruments designated as cash flow hedges
The amount of gain (loss) recognized in interest and other income, net	$ (140)	$ 13