Supplemental Information On Oil And Natural Gas Producing Activities (Standardized Measure) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental Information On Oil And Natural Gas Producing Activities
Future cash inflows	$ 182,612	$ 289,767
Future production costs	(102,569)	(165,861)
Future estimated development costs	(8,872)	(19,026)
Future net cash flows	71,171	104,880
10% annual discount for estimated timing of cash flows	(21,535)	(37,028)
Standardized measure of discounted future net cash flows related to proved gas reserves	$ 49,636	$ 67,852	$ 119,533