Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Assets, Current [Abstract]
Cash and cash equivalents	$ 5,092	$ 10,664
Restricted cash	117	119
Oil and gas revenue receivable	98,325	84,095
Joint interest billing and other receivables	26,139	17,725
Derivative assets	0	1,415
Other current assets	15,105	14,613
Assets, Current	144,778	128,631
Oil And Gas Properties Net Using Full Cost Method Of Accounting [Abstract]
Proven	2,178,293	2,008,538
Unproven properties not being amortized	399,027	413,073
Property, plant and equipment, net	219,691	216,909
Deferred tax assets	6	6
Deferred financing costs and other	16,338	18,162
Assets	2,958,133	2,785,319
Liabilities, Current [Abstract]
Accounts payable	59,478	54,806
Accrued liabilities	85,746	79,811
Current portion of long term debt	100,000	0
Production taxes payable	46,717	40,538
Interest payable	31,427	31,865
Derivative Liabilities, Current	40,007	27,291
Capital cost accrual	134,329	173,165
Liabilities, Current	497,704	407,476
Long-term debt	2,337,000	2,470,000
Deferred gain on sale of liquids gathering system	142,124	147,401
Other long-term obligations	104,830	91,932
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common Stock, Value, Issued	489,362	487,273
Treasury Stock, Value	(37)	(1,961)
Retained loss	(612,850)	(816,802)
Total shareholders' deficit	(123,525)	(331,490)
Liabilities and Stockholders' Equity	$ 2,958,133	$ 2,785,319