Supplemental Oil And Gas Disclosures (Schedule Of The Oil And Natural Gas Property Costs Not Being Amortized) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Unproved properties acquired and wells in progress	$ 330,216	$ 296,764	$ 314,867
2018
Unproved properties acquired and wells in progress	60,372
2017
Unproved properties acquired and wells in progress	46,986
2016
Unproved properties acquired and wells in progress	21,947
2015 and prior
Unproved properties acquired and wells in progress	$ 200,911