Condensed Consolidated Statements of Cash Flows Condensed Consolidated Statement of Cash Flows (Supplemental Disclosure) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Cash and Cash Equivalents, at Carrying Value	$ 208	$ 188	$ 195
Restricted Cash and Cash Equivalents, Current	756	803	255
Restricted Cash and Cash Equivalents, Noncurrent	31	26	27
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 994	$ 1,017	$ 476	$ 487