Balance Sheet Parenthetical (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Oil and Gas Property, Successful Effort Method, Accumulated Depreciation, Depletion and Amortization	$ 3,385,234	$ 3,481,836
Property, Plant and Equipment, Other, Accumulated Depreciation	$ 34,699	$ 32,956
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	200,000,000	200,000,000
Common Stock, Shares, Issued	68,077,546	68,075,700
Common Stock, Shares, Outstanding	68,077,546	68,075,700
Assets Held-for-sale [Member]
Oil and Gas Property, Successful Effort Method, Accumulated Depreciation, Depletion and Amortization	$ 288,592	$ 0