Stockholders' equity (Reclassifications out of AOCI) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest and other income, net	$ 185	$ 231
Income before income taxes	2,314	2,619
Provision for income taxes	(322)	(308)
Net income	1,992	2,311
Product sales [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Product sales	5,286	5,343
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	(28)	130
Provision for income taxes	6	(28)
Net income	(22)	102
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	(4)	(134)
Provision for income taxes	0	1
Net income	(4)	(133)
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	14
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	(42)
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	(28)	130
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	14	(34)
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	$ (42)	$ 164

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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