Stockholders' equity (Reclassifications out of AOCI) (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest and other income, net	$ 55			$ 114			$ 69	$ 517
Income before income taxes	2,206			2,277			6,256	7,155
Provision for income taxes	(185)			(309)			(607)	(1,016)
Net income	2,021	$ 1,803	$ 1,825	1,968	$ 2,179	$ 1,992	5,649	6,139
Product sales [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Product sales	6,104			5,463			17,906	16,323
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	224			(38)			259	(30)
Provision for income taxes	(49)			8			(57)	6
Net income	175			(30)			202	(24)
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	0			(3)			33	(9)
Provision for income taxes	0			0			(7)	0
Net income	0			(3)			26	(9)
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	41			26			158	62
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	183			(64)			101	(92)
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	41			26			158	62
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	$ 183			$ (64)			$ 101	$ (92)