CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Current assets:
Cash and cash equivalents	$ 101,080	$ 5,077
Accounts receivable	173,557	163,190
Refundable income taxes	3,134	8,482
Prepaid expenses and other	32,281	45,522
Derivative asset	28,985	43,491
Deferred income taxes	7,086	8,883
Total current assets	346,123	274,645
Property and equipment (successful efforts method), at cost:
Land	1,526	1,491
Proved oil and gas properties	3,799,844	3,389,158
Less - accumulated depletion, depreciation, and amortization	(1,532,670)	(1,326,932)
Unproved oil and gas properties	89,317	94,290
Wells in progress	245,650	145,327
Materials inventory, at lower of cost or market	15,915	22,542
Oil and gas properties held for sale (note 3)	130,077	86,811
Other property and equipment, net of accumulated depreciation of $17,550 in 2011 and $15,480 in 2010	61,831	21,365
Total property and equipment (successful efforts method)	2,811,490	2,434,052
Other noncurrent assets:
Derivative asset	10,624	18,841
Other noncurrent assets	51,656	16,783
Total other noncurrent assets	62,280	35,624
Total Assets	3,219,893	2,744,321
Current liabilities:
Accounts payable and accrued expenses	413,048	417,654
Derivative liability	70,100	82,044
Deposit associated with oil and gas properties held for sale		2,355
Total current liabilities	483,148	502,053
Noncurrent liabilities:
Long-term credit facility		48,000
3.50% Senior Convertible Notes, net of unamortized discount of $7,209 in 2011 and $11,827 in 2010	280,291	275,673
6.625% Senior Notes	350,000
Asset retirement obligation	72,273	69,052
Asset retirement obligation associated with oil and gas properties held for sale (note 3)	92	2,119
Net Profits Plan liability	133,419	135,850
Deferred income taxes	496,405	443,135
Derivative liability	38,233	32,557
Other noncurrent liabilities	16,866	17,356
Total noncurrent liabilities	1,387,579	1,023,742
Commitments and contingencies (note 7)
Stockholders' equity:
Common stock, $0.01 par value - authorized: 200,000,000 shares; issued: 63,764,421 shares in 2011 and 63,412,800 shares in 2010; outstanding, net of treasury shares: 63,683,354 shares in 2011 and 63,310,165 shares in 2010	638	634
Additional paid-in capital	215,704	191,674
Treasury stock, at cost: 81,067 shares in 2011 and 102,635 shares in 2010	(1,544)	(423)
Retained earnings	1,144,972	1,042,123
Accumulated other comprehensive loss	(10,604)	(15,482)
Total stockholders' equity	1,349,166	1,218,526
Total Liabilities and Stockholders' Equity	$ 3,219,893	$ 2,744,321