Description of Business, Including Segment and Geographic Area Information - Schedule of Revenue by Geographic Area (Parenthetical) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Revenue	$ 4,017	$ 3,693	$ 7,806	$ 7,095
China (including Hong Kong)
Segment Reporting Information [Line Items]
Revenue	$ 1,700	$ 1,600	$ 3,300	$ 3,100