Supplemental Information To Statements Of Cash Flows (Schedule Of Supplemental Information To Statements Of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Net change in working capital accounts, net of assets and liabilities assumed:
Accounts receivable	$ 146	$ 404
Other current assets	366	332
Accounts payable	(121)	(15)
Revenues and royalties payable	(101)	(236)
Other current liabilities	(92)	(270)
Net change in working capital	198	215
Interest paid (net of capitalized interest)	115	118
Income taxes paid (received)	$ (128)	$ (414)