Segment and Related Information - Revenue by Geographic Region (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 1,609	$ 1,509	$ 3,176	$ 2,962
U.S.
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	960	921	1,911	1,812
European region
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	404	361	785	706
Asia
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	158	142	315	276
Rest of the world
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 87	$ 85	$ 165	$ 168