Oil And Natural Gas Properties And Related Equipment (Properties) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Oil And Natural Gas Properties And Related Equipment.
Proved property	$ 200,422	$ 758,366
Unproved property	49	46
Land		501
Total property costs	200,471	758,913
Materials and supplies		1,056
Total	200,471	759,969
Less: Accumulated depreciation, depletion, amortization and impairments	(137,420)	(674,338)
Oil and natural gas properties and equipment, net	$ 63,051	$ 85,631