Supplemental financial information - Restructuring Reserve (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Restructuring And Related Activities [Abstract]
Balance, December 31, 2017	$ 29
Restructuring charges	1
Non-cash items	1	[1]
Payments	(2)
Balance, March 31, 2018	$ 29

[1] Reflects charges for impacts of accelerated depreciation and changes in exchange rates.