Basis of Presentation and Principles of Consolidation Basis of Presentation and Principles of Consolidation - Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 1,454	$ 1,513
Restricted Cash and Cash Equivalents, Current	3,041	3,113
Restricted Cash and Cash Equivalents, Noncurrent	105	5
Cash, Cash Equivalents And Restricted Cash	$ 4,600	$ 4,631	$ 1,415	$ 1,394