Goodwill and other intangible assets (Identifiable Intangible Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross carrying amounts	$ 18,801	$ 18,344
Accumulated amortization	(11,075)	(10,121)
Intangible assets, net	7,726	8,223
Gross carrying amount	18,857	18,730
Accumulated amortization	(11,075)	(10,121)
Intangible assets, net	7,782	8,609
In-process Research and Development [Member]
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	56	386
Developed-Product-Technology Rights [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amounts	12,586	12,589
Accumulated amortization	(7,312)	(6,796)
Intangible assets, net	5,274	5,793
Licensing Rights [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amounts	3,771	3,275
Accumulated amortization	(1,921)	(1,601)
Intangible assets, net	1,850	1,674
Marketing-Related Rights [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amounts	1,285	1,319
Accumulated amortization	(982)	(920)
Intangible assets, net	303	399
R&D Technology Rights [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amounts	1,159	1,161
Accumulated amortization	(860)	(804)
Intangible assets, net	$ 299	$ 357