Supplemental Information To Statements Of Cash Flows (Schedule Of Supplemental Information To Statements Of Cash Flows) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Changes in assets and liabilities, net:
Accounts receivable	$ 231	$ (3)	$ (69)
Other current assets	(97)	(7)	(152)
Other long-term assets	(9)	17	(7)
Accounts payable	(38)	(54)	(3)
Revenues and royalties payable	(71)	8	106
Other current liabilities	(68)	(66)	3
Other long-term liabilities	(43)	23	(36)
Total	(95)	(82)	(158)
Supplementary cash flow data - total operations:
Interest paid	259	308	385
Income taxes paid	$ 171	$ 6	$ 40