CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (in thousands, except share amounts) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Assets
Cash and cash equivalents	$ 236,435	$ 282,248
Accounts receivable	307,784	318,371
Derivative asset	7,450	21,559
Deferred income taxes	11,227	10,749
Prepaid expense and other	14,446	14,574
Total current assets	577,342	647,501
Proved oil and gas properties	5,875,541	5,637,462
Less - accumulated depletion, depreciation, and amortization	(2,722,287)	(2,583,698)
Unproved oil and gas properties	287,607	271,100
Wells in progress	277,879	279,654
Oil and gas properties held for sale net of accumulated depletion, depreciation and amortization of $31,776 in 2014 and $7,390 in 2013	42,276	19,072
Other property and equipment, net of accumulated depreciation of $31,013 in 2014 and $28,775 in 2013	243,680	236,202
Total property and equipment, net	4,004,696	3,859,792
Derivative asset	13,886	30,951
Restricted cash	23,753	96,713
Other noncurrent assets	69,334	70,208
Total other noncurrent assets	106,973	197,872
Total Assets	4,689,011	4,705,165
Liabilities
Accounts payable and accrued expenses	443,395	606,751
Derivative liability	60,684	26,380
Other current liabilities	11,200	6,000
Total current liabilities	515,279	639,131
Revolving credit facility	0	0
Senior Notes (note 5)	1,600,000	1,600,000
Asset retirement obligation	115,889	115,659
Asset retirement obligation associated with oil and gas properties held for sale	4,526	3,033
Net Profits Plan liability	55,209	56,985
Deferred income taxes	688,994	650,125
Derivatives liability	7,885	4,640
Other noncurrent liabilities	25,810	28,771
Total noncurrent liabilities	2,498,313	2,459,213
Commitments and contingencies (note 6)
Stockholders' equity:
Common stock, $0.01 par value - authorized: 200,000,000 shares; issued: 67,078,853 shares in 2014 and 67,078,853 shares in 2013; outstanding, net of treasury shares: 67,056,441 shares in 2014 and 67,056,441 shares in 2013	671	671
Additional paid-in-capital	264,064	257,720
Treasury stock, at cost: 22,412 shares in 2014 and 22,412 in 2013	(823)	(823)
Retained earnings	1,416,923	1,354,669
Accumulated other comprehensive loss	(5,416)	(5,416)
Total stockholders' equity	1,675,419	1,606,821
Total Liabilities and Stockholders' Equity	$ 4,689,011	$ 4,705,165