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, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Oil And Gas Information [Abstract]
Future cash inflows	$ 65,871	$ 39,889	$ 27,253
Future production costs and taxes	(35,877)	(23,343)	(16,270)
Future development costs	(2,833)	(1,586)	(553)
Future net cash flows	27,161	14,960	10,430
Discount at 10% for timing of cash flows	(13,185)	(6,790)	(4,615)
Standardized measure of discounted future net cash flows	$ 13,976	$ 8,170	$ 5,815	$ 8,287