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, 2016	Dec. 31, 2015	Dec. 31, 2014
Net change in working capital accounts, net of assets and liabilities assumed:
Accounts receivable	$ (176)	$ 942	$ 128
Income taxes receivable	130	384	(467)
Other current assets	215	(57)	(222)
Accounts payable	(167)	(190)	(68)
Revenues and royalties payable	96	(526)	133
Other current liabilities	(106)	(864)	546
Net change in working capital	(8)	(311)	50
Interest paid (net of capitalized interest)	566	494	514
Income taxes paid (received)	$ (159)	$ (279)	$ 899