Business combinations (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2015	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill	$ 14,761	$ 14,787	$ 14,751
Dezima [Member]
Business Acquisition [Line Items]
Consideration transferred		410
Contingent consideration obligations in connection with business combinations	0	110
Indefinite-lived intangible assets - IPR&D		400
Goodwill		108
Deferred tax liabilities		$ 100
IPR&D impairment charge	400
Net changes in valuation	$ 116