CONDENSED CONSOLIDATED BALANCE SHEET (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013		Mar. 31, 2013	Dec. 31, 2012		Jun. 30, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 226,372			$ 279,526		$ 223,849	$ 38,451
Accounts receivable	166,150			167,288
Fair value of hedging contracts	30,053			39,655
Current income tax receivable	26,530			10,027
Deferred taxes	15,653	[1]		15,514	[1]
Inventory	4,006			4,207
Other current assets	3,872			3,626
Total current assets	472,636			519,843
Oil and gas properties, full cost method of accounting:
Proved	7,478,481			7,244,466
Less: accumulated depreciation, depletion and amortization	(5,671,005)			(5,510,166)
Net proved oil and gas properties	1,807,476			1,734,300
Unevaluated	534,979			447,795
Other property and equipment, net	22,517			22,115
Fair value of hedging contracts	13,221			9,199
Other assets, net	55,066			43,179
Total assets	2,905,895			2,776,431
Current liabilities:
Accounts payable to vendors	93,965			94,361
Undistributed oil and gas proceeds	27,280			23,414
Accrued interest	18,059			18,546
Fair value of hedging contracts	1,880			149
Asset retirement obligations	63,646			66,260
Other current liabilities	9,705			16,765
Total current liabilities	214,535			219,495
Long-term debt	920,485			914,126
Deferred taxes	366,077	[1]		310,830	[1]
Asset retirement obligations	420,417			422,042
Fair value of hedging contracts	436			1,530
Other long-term liabilities	32,909			36,275
Total liabilities	1,954,859			1,904,298
Commitments and contingencies
Stockholders' equity:
Common stock, $.01 par value; authorized 100,000,000 shares; issued 48,728,810 and 48,392,552 shares, respectively	487			484
Treasury stock (16,582 shares, at cost)	(860)			(860)
Additional paid-in capital	1,389,898			1,386,475
Accumulated deficit	(463,019)			(542,799)
Accumulated other comprehensive income	24,530		10,500	28,833
Total stockholders' equity	951,036			872,133
Total liabilities and stockholders' equity	$ 2,905,895			$ 2,776,431

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