Derivative instruments (Locations and Effective Portions of Gain (Loss) Reclassified out of AOCI) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative Instruments Gain Loss [Line Items]
Product sales	$ 5,663	$ 5,516	$ 5,474	$ 5,239	$ 5,329	$ 5,516	$ 5,225	$ 4,874	$ 21,892	$ 20,944	$ 19,327
Interest and other income, net									629	603	465
Interest expense, net									(1,260)	(1,095)	(1,071)
Income before income taxes									9,163	7,978	5,585
Accumulated net gain (loss) from designated or qualifying cash flow hedges [Member] | Reclassification out of AOCI [Member]
Derivative Instruments Gain Loss [Line Items]
Product sales									308	326	28
Interest and other income, net									(446)	(182)	(230)
Interest expense, net									(1)	(1)	(1)
Income before income taxes									(139)	143	(203)
Accumulated net gain (loss) from designated or qualifying cash flow hedges [Member] | Reclassification out of AOCI [Member] | Derivatives in cash flow hedging relationships [Member]
Derivative Instruments Gain Loss [Line Items]
Income before income taxes									(139)	143	(203)
Accumulated net gain (loss) from designated or qualifying cash flow hedges [Member] | Reclassification out of AOCI [Member] | Derivatives in cash flow hedging relationships [Member] | Foreign currency contracts [Member]
Derivative Instruments Gain Loss [Line Items]
Product sales									308	326	28
Accumulated net gain (loss) from designated or qualifying cash flow hedges [Member] | Reclassification out of AOCI [Member] | Derivatives in cash flow hedging relationships [Member] | Cross-currency swap contracts [Member]
Derivative Instruments Gain Loss [Line Items]
Interest and other income, net									(446)	(182)	(230)
Accumulated net gain (loss) from designated or qualifying cash flow hedges [Member] | Reclassification out of AOCI [Member] | Derivatives in cash flow hedging relationships [Member] | Forward interest rate contract [Member]
Derivative Instruments Gain Loss [Line Items]
Interest expense, net									$ (1)	$ (1)	$ (1)