Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 12,921	$ 11,307
Restricted cash	121	121
Oil and gas revenue receivable	81,143	88,243
Joint interest billing and other receivables	26,712	82,370
Derivative assets	0	230,385
Prepaid drilling costs and other current assets	4,951	7,494
Total current assets	125,848	419,920
Oil And Gas Properties, Net, Using Full Cost Method Of Accounting [Abstract]
Proven	1,657,500	3,651,622
Unproven properties not being amortized	0	537,526
Property, plant and equipment	212,372	246,586
Long Term Derivative Assets	0	0
Deferred financing costs and other	11,625	14,051
Total assets	2,007,345	4,869,705
Current liabilities:
Accounts payable	67,489	105,453
AccruedLiabilitiesCurrent	121,124	190,420
Production taxes payable	47,745	62,117
Interest Payable Current	30,093	30,306
Current deferred tax liabilities	0	73,380
Derivative liabilities	0	0
Capital cost accrual	247,641	209,303
Total current liabilities	514,092	670,979
Long-term debt	1,837,000	1,903,000
Non-current derivative liability	0	0
Deferred income tax liability	0	635,009
Deferred gain on sale of liquids gathering system	158,082	0
Other long-term obligations	76,038	67,008
CommitmentsAndContingencies
Shareholders' equity:
Common stock - no par value; authorized - unlimited; issued and outstanding - 152,476,564 and 152,567,813, respectively	474,016	463,221
Treasury stock	(13)	(14,951)
Retained earnings	(1,051,870)	1,145,439
Total Shareholders' (Deficit) Equity	(577,867)	1,593,709
Total liabilities and shareholders' equity	$ 2,007,345	$ 4,869,705