CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 877	$ 3,012
Accounts receivable	72,734	79,089
Derivative instruments	107,500	89,621
Other current assets	40,241	38,950
Total current assets	221,352	210,672
Oil and gas properties, full cost method of accounting:
Proved, net of accumulated depletion of $7,002,621 and $6,901,997	2,063,359	1,923,145
Unproved	666,382	675,995
Net oil and gas properties	2,729,741	2,599,140
Other property and equipment, net of accumulated depreciation and amortization of $49,574 and $47,989	52,470	51,976
Net property and equipment	2,782,211	2,651,116
Deferred income taxes	229,293	231,116
Goodwill	239,420	239,420
Derivative instruments	22,040	10,422
Other assets	36,958	38,405
TOTAL ASSETS	3,531,274	3,381,151
Current liabilities:
Accounts payable and accrued liabilities	224,502	247,880
Accrued interest	28,669	23,259
Derivative instruments	45,467	28,944
Deferred income taxes	19,667	20,172
Other current liabilities	46,005	20,582
Total current liabilities	364,310	340,837
Long-term debt	1,804,481	1,693,044
Asset retirement obligations	75,659	77,898
Derivative instruments	7,663	0
Other liabilities	76,757	76,259
Total liabilities	2,328,870	2,188,038
Shareholders' equity:
Preferred stock, none issued and outstanding	0	0
Common stock, 117,741,791 and 114,525,673 shares issued and outstanding	11,774	11,454
Capital surplus	2,528,451	2,486,994
Accumulated deficit	(1,319,736)	(1,287,063)
Accumulated other comprehensive loss	(18,085)	(18,272)
Total shareholders' equity	1,202,404	1,193,113
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 3,531,274	$ 3,381,151