Supplemental Information On Oil And Natural Gas Producing Activities (Standardized Measure) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Supplemental Information On Oil And Natural Gas Producing Activities [Abstract]
Future cash inflows	$ 289,767	$ 532,152
Future production costs	(165,861)	(260,909)
Future estimated development costs	(19,026)	(57,741)
Future net cash flows	104,880	213,502
10% annual discount for estimated timing of cash flows	(37,028)	(93,969)
Standardized measure of discounted future net cash flows related to proved gas reserves	$ 67,852	$ 119,533	$ 143,714