Company Restructuring - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges	$ 27	$ 53	$ 49	$ 63
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	$ 109		$ 109