CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
ASSETS
Cash and Cash Equivalents	$ 87	$ 5,926
Accounts Receivable	255,888	254,805
Refundable income taxes	3,113	3,364
Prepaid Expense and Other Assets	28,523	30,017
Derivative Assets	23,364	37,873
Deferred income taxes	9,215	8,579
Total current assets	320,190	340,564
Land	1,857	1,845
Proved Oil and Gas Properties	5,670,183	5,401,684
Less - accumulated depletion, depreciation, and amortization	(2,564,865)	(2,376,170)
Unproved oil and gas properties	173,215	175,287
Wells in Progress	296,854	273,928
Materials inventory, at lower of cost or market	14,110	13,444
Oil and gas properties held for sale net of accumulated depletion, depreciation and amortization of $21,305 in 2013 and 20,676 in 2012	33,340	33,620
Other property and equipment, net of accumulated depreciation of $23,968 in 2013 and $22,442 in 2012	156,416	153,559
Total property and equipment, net	3,781,110	3,677,197
Derivative asset	8,571	16,466
Restricted cash	106,800	86,773
Other noncurrent assets	75,653	78,529
Total other noncurrent assets	191,024	181,768
Total Assets	4,292,324	4,199,529
Accounts payable and accrued expenses	480,318	525,627
Derivative liability	22,836	8,999
Other current liabilities	7,000	6,920
Total current liabilities	510,154	541,546
Long-term credit facility	430,000	340,000
6.625% Senior Notes, Due 2019	350,000	350,000
6.50% Senior Notes, Due 2021	350,000	350,000
6.50% Senior Notes, Due 2023	400,000	400,000
Asset retirement obligations	115,163	112,912
Asset retirement obligations associated with oil and gas properties held for sale	4,396	1,393
Net Profits Plan liability	76,902	78,827
Deferred income taxes	548,339	537,383
Derivatives liability	12,669	6,645
Other noncurrent liabilities	57,876	66,357
Total noncurrent liabilities	2,345,345	2,243,517
Commitments and Contingencies (note 6)
Stockholders' equity:
Common stock, $0.01 par value - authorized: 200,000,000 shares; issued: 66,300,003 shares in 2013 and 66,245,816 shares in 2012; outstanding, net of treasury shares: 66,249,422 shares in 2013 and 66,195,235 shares in 2012	663	662
Additional paid-in-capital	242,526	233,642
Treasury Stock, at cost: 50,581 shares in 2013 and 2012	(1,221)	(1,221)
Retained Earnings	1,203,813	1,190,397
Accumulated other comprehensive loss	(8,956)	(9,014)
Total stockholders' equity	1,436,825	1,414,466
Total Liabilities and Stockholders' Equity	$ 4,292,324	$ 4,199,529