Restructuring Charges/Other - Restructuring Reserve (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring And Related Activities [Abstract]
Balance, January 1		$ 40	$ 32	$ 57
Restructuring charges	[1]	11	25	14
Non-cash items	[2]	(1)	(6)	0
Payments		(21)	(11)	(39)
Balance, December 31		$ 29	$ 40	$ 32

[1] Includes severance and benefits, accelerated depreciation, changes in estimates or other exit costs.

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