Supplemental Information On Oil And Natural Gas Producing Activities (Change Standardized Measure) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Supplemental Information On Oil And Natural Gas Producing Activities [Abstract]
Beginning of the period	$ 119,533	$ 143,714
Sales and transfers of oil and natural gas, net of production costs	(30,748)	(38,817)
Net changes in prices and production costs related to future production	(125,979)	(18,410)
Development costs incurred during the period	5,016	18,075
Changes in extensions and discoveries	178	24,611
Revisions of previous quantity estimates	(11,299)	(22,034)
Purchases and sales of reserves in place	109,181	1,918
Accretion discount	11,953	14,371
Other	(9,983)	(3,895)
Standardized measure of discount future net cash flows related to proved gas reserves	$ 67,852	$ 119,533