Stockholders' equity (Reclassifications out of AOCI) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest and other income, net	$ 162	$ 165	$ 393	$ 360
Income before income taxes	2,647	2,542	5,266	5,002
Provision for income taxes	(351)	(391)	(659)	(780)
Net income	2,296	2,151	4,607	4,222
Product sales [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Product sales	5,679	5,574	11,022	10,773
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Cash flow hedges [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	(318)	330	(188)	461
Provision for income taxes	68	(117)	40	(164)
Net income	(250)	213	(148)	297
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	(115)	(47)	(249)	(96)
Provision for income taxes	1	(2)	2	(2)
Net income	(114)	(49)	(247)	(98)
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Foreign currency contract [Member] \| Cash flow hedges [Member] \| Product sales [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Product sales	(20)		(54)
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Cross-currency swap contract [Member] \| Cash flow hedges [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest and other income, net	(298)		(134)
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Cash flow hedges [Member] \| Cash flow hedges [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	(318)	330	(188)	461
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Cash flow hedges [Member] \| Foreign currency contract [Member] \| Cash flow hedges [Member] \| Product sales [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Product sales	(20)	33	(54)	90
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Cash flow hedges [Member] \| Cross-currency swap contract [Member] \| Cash flow hedges [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest and other income, net	$ (298)	$ 297	$ (134)	$ 371

Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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