Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Assets, Current [Abstract]
Cash and Cash Equivalents, at Carrying Value	$ 14,367	$ 12,921
Restricted cash	119	121
Oil and gas revenue receivable	81,127	81,143
Oil and Gas Joint Interest Billing Receivables, Current	29,327	26,712
Prepaid drilling costs and other current assets	4,123	4,951
Assets, Current	129,063	125,848
Oil And Gas Properties Net Using Full Cost Method Of Accounting [Abstract]
Proven	1,683,696	1,657,500
Property, Plant and Equipment, Net	211,535	212,372
Other Assets, Noncurrent	11,089	11,625
Assets	2,035,383	2,007,345
Liabilities, Current [Abstract]
Accounts payable	59,245	67,489
Accrued liabilities	75,849	121,124
Production taxes payable	47,813	47,745
Interest Payable	8,903	30,093
Derivative Liabilities, Current	44,715	0
Capital cost accrual	185,569	247,641
Liabilities, Current	422,094	514,092
Long-term Debt, Excluding Current Maturities	1,933,000	1,837,000
Deferred gain on sale of liquids gathering system	155,415	158,082
Other Liabilities, Noncurrent	87,066	76,038
Commitments and Contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common Stock, Value, Issued	478,343	474,016
Treasury Stock, Value	(3,297)	(13)
Retained Earnings (Accumulated Deficit)	(1,037,238)	(1,051,870)
Stockholders' Equity Attributable to Parent	(562,192)	(577,867)
Liabilities and Stockholders' Equity	$ 2,035,383	$ 2,007,345