Stockholders' equity (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Product sales	$ 4,595	$ 4,200	$ 8,746	$ 8,101
Interest and other income, net	96	124	260	248
Interest expense, net	(241)	(256)	(504)	(491)
Income before income taxes	1,405	1,457	2,748	2,823
Tax (expense)/benefit	(147)	(191)	(56)	(373)
Net income	1,258	1,266	2,692	2,450
Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Product sales	7		3
Interest and other income, net	12		(128)
Interest expense, net	(1)		(1)
Income before income taxes	18	0	(126)	24
Tax (expense)/benefit	(7)		46
Net income	11		(80)
Realized Gains and Losses on Available-for-sale Securities [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest and other income, net	7		74
Tax (expense)/benefit	(3)		(28)
Net income	$ 4		$ 46