Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Assets, Current [Abstract]
Cash and cash equivalents	$ 7,980	$ 10,664
Restricted cash	117	119
Oil and gas revenue receivable	118,619	84,095
Joint interest billing and other receivables	15,354	17,725
Derivative assets	290	1,415
Other current assets	15,669	14,613
Assets, Current	158,029	128,631
Oil And Gas Properties Net Using Full Cost Method Of Accounting [Abstract]
Proven	2,078,355	2,008,538
Unproven properties not being amortized	410,264	413,073
Property, plant and equipment, net	217,862	216,909
Deferred tax assets	6	6
Deferred financing costs and other	17,326	18,162
Assets	2,881,842	2,785,319
Liabilities, Current [Abstract]
Accounts payable	51,759	54,806
Accrued liabilities	89,395	79,811
Current portion of long term debt	100,000	0
Production taxes payable	43,863	40,538
Interest payable	16,366	31,865
Derivative Liabilities, Current	62,486	27,291
Capital cost accrual	168,970	173,165
Liabilities, Current	532,839	407,476
Long-term debt	2,325,000	2,470,000
Deferred gain on sale of liquids gathering system	144,762	147,401
Other long-term obligations	106,939	91,932
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common Stock, Value, Issued	490,748	487,273
Treasury Stock, Value	(1,451)	(1,961)
Retained loss	(716,995)	(816,802)
Total shareholders' deficit	(227,698)	(331,490)
Liabilities and Stockholders' Equity	$ 2,881,842	$ 2,785,319