Supplemental Information To Statements Of Cash Flows (Schedule Of Supplemental Information To Statements Of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Changes in assets and liabilities, net
Accounts receivable	$ (188)	$ 46	$ (151)	$ 74
Other current assets	(7)	11	(95)	(13)
Other long-term assets	(28)	9	(81)	10
Accounts payable	78	51	82	68
Revenues and royalties payable	146	(45)	212	51
Other current liabilities	(127)	34	(63)	(52)
Other long-term liabilities	(7)	(4)	(12)	(5)
Total	(133)	102	(108)	133
Supplementary cash flow data - total operations:
Interest paid (net of capitalized interest)	138	144	214	236
Income taxes received	$ (7)	$ (4)	$ (6)	$ (1)