CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 286	$ 119,194
Accounts receivable	224,335	210,368
Refundable income taxes	2,575	5,581
Prepaid expenses and other	44,141	68,026
Derivative asset	67,457	55,813
Deferred income taxes	4,950	4,222
Total current assets	343,744	463,204
Property and equipment (successful efforts method), at cost:
Land	1,550	1,548
Proved Oil and Gas Property, Successful Effort Method	4,657,347	4,378,987
Less - accumulated depletion, depreciation, and amortization	(1,888,104)	(1,766,445)
Unproved Oil and Gas Property, Successful Effort Method	130,688	120,966
Wells in progress	213,280	273,428
Materials inventory, at lower of cost or market	14,150	16,537
Oil and gas properties held for sale (note 3)	42,189	246
Other property and equipment, net of accumulated depreciation of $25,048 in 2012 and $23,985 in 2011	106,904	71,369
Total property and equipment, net	3,278,004	3,096,636
Other noncurrent assets:
Derivative asset	30,595	31,062
Restricted Cash and Cash Equivalents, Noncurrent	114,343	124,703
Other noncurrent assets	78,412	83,375
Total other noncurrent assets	223,350	239,140
Total Assets	3,845,098	3,798,980
Current liabilities:
Accounts payable and accrued expenses	413,211	456,999
Derivative liability	50,764	42,806
Deposit associated with oil and gas properties held for sale	7,550	6,000
Total current liabilities	471,525	505,805
Noncurrent liabilities:
Long-term credit facility	24,000	0
3.50% Senior Convertible Notes, net of unamortized discount of $0 in 2012 and $2,431 in 2011	287,500	285,069
Senior Notes, 6.625%, Noncurrent	350,000	350,000
Senior Notes, 6.50%, Noncurrent	350,000	350,000
Asset retirement obligation	87,647	87,167
Asset retirement obligation associated with oil and gas properties held for sale (note 3)	1,770	1,277
Net Profits Plan liability	111,670	107,731
Deferred income taxes	583,660	568,263
Derivative liability	25,397	12,875
Other noncurrent liabilities	61,505	67,853
Total noncurrent liabilities	1,883,149	1,830,235
Commitments and contingencies (note 7)
Stockholders' equity:
Common stock, $0.01 par value - authorized: 200,000,000 shares; issued: 64,231,114 shares in 2012 and 64,145,482 shares in 2011; outstanding, net of treasury shares: 64,150,047 shares in 2012 and 64,064,415 shares in 2011	642	641
Additional paid-in capital	222,353	216,966
Treasury stock, at cost: 81,067 shares in 2012 and 102,635 shares in 2011	(1,544)	(1,544)
Retained earnings	1,274,287	1,251,157
Accumulated other comprehensive loss	(5,314)	(4,280)
Total stockholders' equity	1,490,424	1,462,940
Total Liabilities and Stockholders' Equity	$ 3,845,098	$ 3,798,980