Supplemental Oil And Gas Information (Schedule Of Standardized Measure Of Discounted Futures Net Cash Flows From Proved Oil And Gas Reserves) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Supplemental Oil And Gas Information [Abstract]
Future cash inflows	$ 27,253	$ 38,566	$ 158,792
Future production costs and taxes	(16,270)	(23,500)	(71,951)
Future development costs	(553)	(951)	(10,014)
Future income tax expenses			(13,092)
Future net cash flows	10,430	14,115	63,735
Discount at 10% for timing of cash flows	(4,615)	(5,828)	(29,204)
Standardized measure of discounted future net cash flows	$ 5,815	$ 8,287	$ 34,531	$ 38,708