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	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Amortization of initial payments for new contracts	$ 65	$ 51	$ 45
Amortization related to equity method investments	$ 47	$ 60	$ 62