Supplemental Oil And Gas Disclosures (Schedule Of Principal Sources Of Changes In Standardized Measure Of Discounted Future Net Cash Flows) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reserve Quantities [Line Items]
Sales and transfers of oil and natural gas produced, net of production costs	$ (200,233)	$ (297,791)	$ (239,953)
Net changes in prices and production costs	(508,066)	120,062	236,126
Revisions in quantity estimates and changes in production timing	(338,994)	(33,282)	87,239
Extensions, discoveries, and improved recovery, less related costs	53,123	234,172	102,965
Changes in estimated future development costs	311,190	19,535	(5,194)
Previously estimated cost incurred during the period	64,362	63,557	36,044
Purchases of minerals in place	6,416	23,416	51,686
Sales of minerals in place	(25,813)	(5,004)	(1,447)
Accretion of discount	110,571	89,753	57,517
Net change in income taxes	121,708	(31,674)	(33,389)
Other-net	(116,233)	(6,236)	(2,634)
Net change	(521,969)	176,508	288,960
Beginning of year	983,678	807,170	518,210
End of year	$ 461,709	$ 983,678	$ 807,170