Company Restructuring - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges	$ 16	$ 14	$ 65	$ 77
Employee costs
Restructuring Cost and Reserve [Line Items]
Cumulative amount incurred to date for active programs	130		130
Exit costs
Restructuring Cost and Reserve [Line Items]
Cumulative amount incurred to date for active programs	$ 110		$ 110