Condensed Consolidated Statements of Cash Flows Condensed Consolidated Statement of Cash Flows (Supplemental Disclosure) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Cash and cash equivalents	$ 139	$ 146	$ 287
Restricted cash and restricted cash equivalents included in Other current assets	2,724	655	850
Restricted cash equivalents included in Other long-term assets	33	27	31
Cash, cash equivalents, restricted cash and restricted cash equivalents at end of period	$ 2,896	$ 829	$ 1,168	$ 1,017