Stockholders' equity (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Product sales	$ 4,799	$ 4,647	$ 4,595	$ 4,151	$ 4,337	$ 4,201	$ 4,200	$ 3,901	$ 18,192	$ 16,639	$ 15,295
Interest and other income, net									420	485	448
Interest expense, net									(1,022)	(1,053)	(610)
Income before income taxes									5,265	5,009	4,150
Tax (expense)									(184)	(664)	(467)
Net income	1,021	1,368	1,258	1,434	788	1,107	1,266	1,184	5,081	4,345	3,683
Cash flow hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Product sales									4
Interest and other income, net									82
Interest expense, net									(1)
Income before income taxes									85
Tax (expense)									(33)
Net income									52
Available-for-sale securities [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest and other income, net									75
Tax (expense)									(28)
Net income									$ 47