CONDENSED CONSOLIDATED BALANCE SHEET (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012		Mar. 31, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 261,353		$ 279,526		$ 263,841	$ 38,451
Accounts receivable	147,336		167,288
Fair value of hedging contracts	18,712		39,655
Current income tax receivable	19,533		10,027
Deferred taxes	23,354	[1]	15,514	[1]
Inventory	4,027		4,207
Other current assets	3,587		3,626
Total current assets	477,902		519,843
Oil and gas properties, full cost method of accounting:
Proved	7,358,370		7,244,466
Less: accumulated depreciation, depletion and amortization	(5,584,698)		(5,510,166)
Net proved oil and gas properties	1,773,672		1,734,300
Unevaluated	471,457		447,795
Other property and equipment, net	22,059		22,115
Fair value of hedging contracts	6,792		9,199
Other assets, net	50,512		43,179
Total assets	2,802,394		2,776,431
Current liabilities:
Accounts payable to vendors	81,491		94,361
Undistributed oil and gas proceeds	28,904		23,414
Accrued interest	15,351		18,546
Fair value of hedging contracts	5,376		149
Asset retirement obligations	68,978		66,260
Other current liabilities	5,840		16,765
Total current liabilities	205,940		219,495
Long-term debt	917,267		914,126
Deferred taxes	336,108	[1]	310,830	[1]
Asset retirement obligations	412,706		422,042
Fair value of hedging contracts	2,997		1,530
Other long-term liabilities	33,853		36,275
Total liabilities	1,908,871		1,904,298
Commitments and contingencies
Stockholders' equity:
Common stock, $.01 par value; authorized 100,000,000 shares; issued 48,683,813 and 48,392,552 shares, respectively	487		484
Treasury stock (16,582 shares, at cost)	(860)		(860)
Additional paid-in capital	1,385,445		1,386,475
Accumulated deficit	(502,041)		(542,799)
Accumulated other comprehensive income	10,492		28,833
Total stockholders' equity	893,523		872,133
Total liabilities and stockholders' equity	$ 2,802,394		$ 2,776,431

[1] Deferred income taxes have been allocated to the guarantor subsidiary where related oil and gas properties reside