Supplemental Oil And Gas Disclosures (Results Of Operations For Producing Activities) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental Oil and Gas Disclosures [Abstract]
Revenues	$ 282,742	$ 371,335	$ 723,566
Production costs	(108,822)	(152,560)	(165,315)
Depreciation, depletion, amortization, and impairment	(268,901)	(1,844,726)	(347,220)
Results of operations, income before income taxes	(94,981)	(1,625,951)	211,031
Income tax (expense) benefit	32,696	612,496	(82,028)
Results of operations for producing activities (excluding corporate overhead and financing costs)	$ (62,285)	$ (1,013,455)	$ 129,003