Stockholders' equity Stockholders' equity (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Product sales	$ 4,151	$ 3,901
Interest and other income, net	164	124
Income before income taxes	1,343	1,366
Income tax (expense)/benefit	91	(182)
Net income	1,434	1,184
Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Product sales	(4)
Interest and other income, net	(140)
Income before income taxes	(144)
Income tax (expense)/benefit	53
Net income	(91)
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	67
Income tax (expense)/benefit	(25)
Net income	$ 42