Supplemental Cash Flow Information (Change in Cash and Cash Equivalents) (Details) - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Cash Flow Elements [Abstract]
Cash and cash equivalents		$ 1,527	$ 1,687
Restricted cash	[1]	2	38
Cash, cash equivalents and restricted cash		$ 1,529	$ 1,725	$ 3,015	$ 892

[1] The restricted cash balance is included within other current assets on the consolidated balance sheets.