Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Interest, net of capitalized interest	$ 61	$ 64
Income taxes, net	16	0
Accounts payable related to capital expenditures	78	57
Cash and cash equivalents	191		$ 238
Total cash, cash equivalents and restricted cash shown in Condensed Statements of Consolidated Cash Flows	229	$ 276	274	$ 381
Other Current Assets [Member]
Restricted cash	37		35
Other Noncurrent Assets [Member]
Restricted cash	$ 1		$ 1