Derivative instruments (Locations and Effective Portions of Gain (Loss) Reclassified out of AOCI) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Derivative Instruments Gain Loss [Line Items]
Product sales	$ 5,574	$ 5,474	$ 10,773	$ 10,713
Interest and other income, net	165	137	360	287
Income before income taxes	2,542	2,204	5,002	4,462
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Derivative Instruments Gain Loss [Line Items]
Product sales	33	79	90	175
Interest and other income, net	297	(212)	371	(142)
Income before income taxes	330	(133)	461	33
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash flow hedge [Member]
Derivative Instruments Gain Loss [Line Items]
Income before income taxes	330	(133)	461	33
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash flow hedge [Member] | Foreign currency contracts [Member]
Derivative Instruments Gain Loss [Line Items]
Product sales	33	79	90	175
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash flow hedge [Member] | Cross currency swap contracts [Member]
Derivative Instruments Gain Loss [Line Items]
Interest and other income, net	$ 297	$ (212)	$ 371	$ (142)