Stockholders' equity (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Product sales	$ 4,647	$ 4,201	$ 13,393	$ 12,302
Interest and other income, net	72	111	332	359
Interest expense, net	(257)	(271)	(761)	(762)
Income before income taxes	1,503	1,263	4,251	4,086
Tax (expense)/benefit	(135)	(156)	(191)	(529)
Net income	1,368	1,107	4,060	3,557
Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Product sales	6		9
Interest and other income, net	153		25
Interest expense, net	0		(1)
Income before income taxes	159	96	33	120
Tax (expense)/benefit	(59)		(13)
Net income	100		20
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	(2)		72
Tax (expense)/benefit	1		(27)
Net income	$ (1)		$ 45