Condensed Consolidated Statements of Cash Flows Condensed Consolidated Statement of Cash Flows (Supplemental Disclosure) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Cash and cash equivalents	$ 123	$ 146	$ 208
Restricted cash and restricted cash equivalents included in Other current assets	2,657	655	756
Restricted cash equivalents included in Other long-term assets	42	27	31
Cash, cash equivalents, restricted cash and restricted cash equivalents at end of period	$ 2,823	$ 829	$ 994	$ 1,017