Supplemental Oil And Gas Disclosures (Standardized Measure Of Discounted Future Cash Flows Relating To Proved Reserves Disclosure) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Future Net Cash Flows Relating to Proved Oil and Gas Reserves, Net Cash Flows [Abstract]
Future cash flows	$ 2,030,925	$ 2,475,898	$ 6,398,236
Future production costs	(861,625)	(1,017,777)	(2,069,636)
Future development costs	(173,446)	(228,445)	(560,102)
Future income tax expenses	(141,752)	(230,544)	(1,228,533)
Future net cash flows	854,102	999,132	2,539,965
10% annual discount for estimated timing of cash flows	(335,892)	(409,646)	(1,104,221)
Standardized measure of discounted future net cash flows relating to proved oil, NGLs and natural gas reserves	$ 518,210	$ 589,486	$ 1,435,744	$ 1,225,976
Percentage of annual discount for estimated timing of cash flows	10.00%	10.00%	10.00%