CONDENSED CONSOLIDATED BALANCE SHEET (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014		Mar. 31, 2014	Dec. 31, 2013		Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 333,886			$ 331,224		$ 226,372		$ 279,526
Accounts receivable	197,495			171,971
Fair value of derivative contracts				4,549
Current income tax receivable	7,372			7,366
Deferred taxes	36,308	[1]		31,710	[1]
Inventory	3,723			3,723
Other current assets	1,955			1,874
Total current assets	580,739			552,417
Oil and gas properties, full cost method of accounting:
Proved	8,520,195			7,804,117
Less: accumulated depreciation, depletion and amortization	(6,144,815)			(5,908,760)
Net proved oil and gas properties	2,375,380			1,895,357
Unevaluated	554,201			724,339
Other property and equipment, net	28,302			26,178
Fair value of derivative contracts	415			1,378
Other assets, net	43,015			48,887
Total assets	3,582,052			3,248,556
Current liabilities:
Accounts payable to vendors	193,900			195,677
Undistributed oil and gas proceeds	62,927			37,029
Accrued interest	9,025			9,022
Fair value of derivative contracts	25,711			7,753
Asset retirement obligations	77,132			67,161
Other current liabilities	79,539			54,520
Total current liabilities	448,234			371,162
Long-term debt	1,033,931			1,027,084
Deferred taxes	404,188	[1]		390,693	[1]
Asset retirement obligations	431,060			435,352
Fair value of derivative contracts	5,251			470
Other long-term liabilities	47,843			53,509
Total liabilities	2,370,507			2,278,270
Commitments and contingencies
Stockholders' equity:
Common stock, $.01 par value; authorized 100,000,000 shares; issued 54,872,749 and 48,750,533 shares, respectively	549			488
Treasury stock (16,582 shares, at cost)	(860)			(860)
Additional paid-in capital	1,624,795			1,397,885
Accumulated deficit	(394,778)			(425,165)
Accumulated other comprehensive income (loss)	(18,161)		(9,200)	(2,062)		24,500	10,500	28,800
Total stockholders' equity	1,211,545			970,286
Total liabilities and stockholders' equity	$ 3,582,052			$ 3,248,556

[1] Deferred income taxes have been allocated to the Guarantor Subsidiary where related oil and gas properties reside.