CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (in thousands, except share amounts) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Assets
Cash and cash equivalents	$ 163,794	$ 282,248
Accounts receivable	312,415	318,371
Derivative asset	3,613	21,559
Deferred income taxes	12,086	10,749
Prepaid expense and other	15,007	14,574
Total current assets	506,915	647,501
Proved oil and gas properties	6,151,765	5,637,462
Less - accumulated depletion, depreciation, and amortization	(2,883,506)	(2,583,698)
Unproved oil and gas properties	388,336	271,100
Wells in progress	495,052	279,654
Oil and gas properties held for sale net of accumulated depletion, depreciation and amortization of $23,697 and $7,390, respectively	23,935	19,072
Other property and equipment, net of accumulated depreciation of $33,529 and $28,775, respectively	258,619	236,202
Total property and equipment, net	4,434,201	3,859,792
Derivative asset	1,300	30,951
Restricted cash	5,499	96,713
Other noncurrent assets	56,120	70,208
Total other noncurrent assets	62,919	197,872
Total Assets	5,004,035	4,705,165
Liabilities
Accounts payable and accrued expenses	592,493	606,751
Derivative liability	92,088	26,380
Other current liabilities	0	6,000
Total current liabilities	684,581	639,131
Revolving credit facility	0	0
Senior Notes (note 5)	1,600,000	1,600,000
Asset retirement obligation	117,916	115,659
Asset retirement obligation associated with oil and gas properties held for sale	2,760	3,033
Net Profits Plan liability	48,104	56,985
Deferred income taxes	725,408	650,125
Derivative liability	52,847	4,640
Other noncurrent liabilities	26,467	28,771
Total noncurrent liabilities	2,573,502	2,459,213
Commitments and contingencies (note 6)
Stockholders' equity:
Common stock, $0.01 par value - authorized: 200,000,000 shares; issued: 67,116,732 and 67,078,853 shares outstanding, respectively; net of treasury shares: 67,116,732 and 67,056,441, respectively	671	671
Additional paid-in-capital	273,664	257,720
Treasury stock, at cost: zero and 22,412 shares, respectively	0	(823)
Retained earnings	1,476,703	1,354,669
Accumulated other comprehensive loss	(5,086)	(5,416)
Total stockholders' equity	1,745,952	1,606,821
Total Liabilities and Stockholders' Equity	$ 5,004,035	$ 4,705,165