Basis of Presentation and Summary of Significant Accounting Policies - Schedule of Amounts Associated with Amortization of Initial Payments for New Contracts and Equity Method Investments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Amortization of initial payments for new contracts	$ 19	$ 16	$ 38	$ 31
Amortization related to equity method investments	$ 12	$ 12	$ 23	$ 21