Supplemental Oil And Gas Information (Schedule Of Reserve Value By Category And The Respective Present Values, Before Income Taxes, Discounted At 10% As A Percentage Of Total Proved Reserves) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reserve Quantities [Line Items]
Total proved reserves year-end reserve report	$ 5,815	$ 8,287	$ 40,417
Proved developed producing reserves (PDP)	$ 5,397	$ 7,686	$ 32,059
% of PDP reserves to total proved reserves	93.00%	93.00%	79.00%
Proved developed non-producing reserves	$ 418	$ 601	$ 2,956
% of PDNP reserves to total proved reserves	7.00%	7.00%	7.00%
Proved undeveloped reserves (PUD)			$ 5,402
% of PUD reserves to total proved reserves			14.00%
Oil [Member]
Reserve Quantities [Line Items]
Total proved reserves year-end reserve report	$ 5,815	$ 8,287	$ 40,417
Proved developed producing reserves (PDP)	$ 5,397	$ 7,686	$ 32,059
% of PDP reserves to total proved reserves	93.00%	93.00%	79.00%
Proved developed non-producing reserves	$ 418	$ 601	$ 2,956
% of PDNP reserves to total proved reserves	7.00%	7.00%	7.00%
Proved undeveloped reserves (PUD)			$ 5,402
% of PUD reserves to total proved reserves			14.00%