Condensed Consolidated Balance Sheet (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010
Current assets:
Cash and cash equivalents	$ 263,841	$ 38,451	$ 45,906	$ 106,956
Accounts receivable	133,266	118,139
Fair value of hedging contracts	24,352	25,177
Current income tax receivable	23,140	19,946
Deferred taxes	30,206	26,072
Inventory	4,643	4,643
Other current assets	754	791
Total current assets	480,202	233,219
Oil and gas properties, full cost method of accounting:
Proved	6,704,772	6,648,168
Less: accumulated depreciation, depletion and amortization	(5,252,894)	(5,174,729)
Net proved oil and gas properties	1,451,878	1,473,439
Unevaluated	443,889	401,609
Other property and equipment, net	11,444	11,172
Fair value of hedging contracts	10,937	22,543
Other assets, net	28,963	23,769
Total assets	2,427,313	2,165,751
Current liabilities:
Accounts payable to vendors	86,307	102,946
Undistributed oil and gas proceeds	26,359	27,328
Accrued interest	10,490	14,059
Fair value of hedging contracts	27,298	11,122
Asset retirement obligations	71,256	62,676
Other current liabilities	10,740	28,370
Total current liabilities	232,450	246,501
Long-term debt	805,140	620,000
Deferred taxes	266,996	247,835
Asset retirement obligations	359,274	363,103
Fair value of hedging contracts	8,025	815
Other long-term liabilities	20,523	19,668
Total liabilities	1,692,408	1,497,922		1,692,408
Commitments and contingencies
Stockholders' equity:
Common stock, $.01 par value; authorized 100,000,000 shares; issued 48,308,879 and 48,076,860 shares, respectively	483	481
Treasury stock (16,582 shares, at cost)	(860)	(860)
Additional paid-in capital	1,376,730	1,338,565
Accumulated deficit	(641,251)	(692,225)
Accumulated other comprehensive income (loss)	(197)	21,868
Total stockholders' equity	734,905	667,829
Total liabilities and stockholders' equity	$ 2,427,313	$ 2,165,751