Balance Sheet Parenthetical (Parentheticals) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Oil and Gas Property, Successful Effort Method, Accumulated Depreciation, Depletion and Amortization	$ 3,240,109	$ 3,233,012
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	67,968,714	67,463,060
Common Stock, Shares, Outstanding	67,968,714	67,463,060
Assets Held-for-sale [Member]
Oil and Gas Property, Successful Effort Method, Accumulated Depreciation, Depletion and Amortization	$ 74,894	$ 22,482
Other Capitalized Property Plant and Equipment [Member]
Oil and Gas Property, Successful Effort Method, Accumulated Depreciation, Depletion and Amortization	$ 43,197	$ 37,079