Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Assets, Current [Abstract]
Cash and Cash Equivalents, at Carrying Value	$ 6,557	$ 12,921
Restricted cash	119	121
Oil and gas revenue receivable	87,622	81,143
Oil and Gas Joint Interest Billing Receivables, Current	17,661	26,712
Derivative Assets, Current	4,027	0
Prepaid drilling costs and other current assets	4,828	4,951
Assets, Current	120,814	125,848
Oil And Gas Properties Net Using Full Cost Method Of Accounting [Abstract]
Proven	1,719,422	1,657,500
Property, Plant and Equipment, Net	212,089	212,372
Other Assets, Noncurrent	10,553	11,625
Assets	2,062,878	2,007,345
Liabilities, Current [Abstract]
Accounts payable	39,623	67,489
Accrued liabilities	87,688	121,124
Production taxes payable	39,266	47,745
Interest Payable	30,333	30,093
Derivative Liabilities, Current	6,887	0
Capital cost accrual	183,607	247,641
Liabilities, Current	387,404	514,092
Long-term Debt, Excluding Current Maturities	1,880,000	1,837,000
Deferred gain on sale of liquids gathering system	152,677	158,082
Other Liabilities, Noncurrent	83,910	76,038
Commitments and Contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common Stock, Value, Issued	482,524	474,016
Treasury Stock, Value	(2,311)	(13)
Retained Earnings (Accumulated Deficit)	(921,326)	(1,051,870)
Stockholders' Equity Attributable to Parent	(441,113)	(577,867)
Liabilities and Stockholders' Equity	$ 2,062,878	$ 2,007,345