Basis of Presentation and Principles of Consolidation - Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 2,677	$ 1,755
Restricted cash, current	119	117
Restricted cash, non-current	10	12
Total cash, cash equivalents, and restricted cash	$ 2,806	$ 1,884	$ 1,566	$ 1,657