Supplementary Oil And Natural Gas Disclosures (Unaudited) (Summary Of Changes In Standardized Measure Of Discounted Future Net Cash Flows Applicable To Proved Oil And Natural Gas Reserves) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Increase (Decrease) in Standardized Measure of Discounted Future Net Cash Flow Relating to Proved Oil and Gas Reserves [Roll Forward]
Beginning of the period	$ 111,050	$ 157,729	$ 303,430
Net change in sales and transfer prices and in production (lifting) costs related to future production	(143,808)	(57,568)	(13,278)
Changes in estimated future development costs	3,787	(5,512)	(48,594)
Sales and transfers of oil and gas produced during the period	(14,779)	(64,316)	(45,866)
Net change due to extensions, discoveries, and improved recovery	6,737		75,304
Net changes due to revisions in quantity estimates	(36,397)	(8,396)	(228,620)
Previously estimated development costs incurred during period	20,636	40,962	10,136
Accretion of discount	17,606	24,251	46,711
Other-unspecified	1,895	4,125	(24,169)
Net change in income taxes	54,336	19,775	82,675
Aggregate change in the standardized measure of discounted future net cash flows for the year	(89,987)	(46,679)	(145,701)
End of the period	$ 21,063	$ 111,050	$ 157,729