Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Current assets:
Cash and cash equivalents	$ 11,307	$ 70,834
Restricted cash	121	98
Oil and gas revenue receivable	88,243	95,142
Joint interest billing and other receivables	82,370	48,561
Derivative assets	230,385	133,991
Inventory	1,164	2,760
Prepaid drilling costs and other current assets	6,330	9,663
Total current assets	419,920	361,049
Oil And Gas Properties, Net, Using Full Cost Method Of Accounting [Abstract]
Proved	3,651,622	2,589,423
Acquisition and exploration costs not being amortized	537,526	486,247
Property, plant and equipment	246,586	149,104
Long Term Derivative Assets	0	2,066
Deferred financing costs and other	14,051	7,726
Total assets	4,869,705	3,595,615
Current liabilities:
Accounts payable and accrued liabilities	295,873	210,311
Production taxes payable	62,117	53,382
Interest Payable Current	30,306	26,878
Current deferred tax liabilities	73,380	42,685
Derivative liabilities	0	718
Capital cost accrual	209,303	84,042
Total current liabilities	670,979	418,016
Long-term debt	1,903,000	1,560,000
Deferred income tax liability	635,009	420,711
Non-current derivative liability	0	5,337
Other long-term obligations	67,008	52,575
Shareholders' equity:
Common stock - no par value; authorized - unlimited; issued and outstanding - 152,476,564 and 152,567,813, respectively	463,221	426,779
Treasury stock	(14,951)	0
Retained earnings	1,145,439	712,197
Total Shareholders' Equity	1,593,709	1,138,976
Total liabilities and shareholders' equity	$ 4,869,705	$ 3,595,615