Stockholders' equity (Reclassifications out of AOCI) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Product sales	$ 5,474	$ 5,225	$ 10,713	$ 10,099
Interest and other income, net	137	198	287	304
Interest expense, net	(313)	(277)	(607)	(529)
Total before income tax	2,204	1,997	4,462	3,873
Tax benefit (expense)	(334)	(344)	(692)	(597)
Net of taxes	1,870	1,653	3,770	3,276
Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedges [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before income tax	(133)	226	33	112
Tax benefit (expense)	49	(81)	(12)	(40)
Net of taxes	(84)	145	21	72
Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedges [Member] | Foreign currency contracts [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Product sales	79	91	175	160
Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedges [Member] | Cross currency swap contracts [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest and other income, net	(212)	136	(142)	(47)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedges [Member] | Forward interest rate contract [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest expense, net	0	(1)	0	(1)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Available-for-sale Securities [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest and other income, net	(23)	(9)	(53)	(44)
Tax benefit (expense)	8	3	8	16
Net of taxes	$ (15)	$ (6)	$ (45)	$ (28)