Supplemental Oil And Gas Disclosures (Schedule Of The Oil And Natural Gas Property Costs Not Being Amortized) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Unproved properties acquired and wells in progress	$ 337,099	$ 485,568	$ 545,588
2015
Unproved properties acquired and wells in progress	49,283
2014
Unproved properties acquired and wells in progress	65,970
2013
Unproved properties acquired and wells in progress	44,607
2012 and prior
Unproved properties acquired and wells in progress	$ 177,239