Goodwill - Changes in the Carrying Amount of Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Balance at beginning of period	$ 1,197	$ 1,196	$ 1,189
Foreign currency translation	(11)	1	7
Balance at end of period	1,186	1,197	1,196
North America [Member]
Goodwill [Roll Forward]
Balance at beginning of period	1,105	1,105	1,105
Foreign currency translation	0	0	0
Balance at end of period	1,105	1,105	1,105
International [Member]
Goodwill [Roll Forward]
Balance at beginning of period	92	91	84
Foreign currency translation	(11)	1	7
Balance at end of period	$ 81	$ 92	$ 91