Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Operating activities
Net (loss) income	$ (15,505)	$ 3,801
Adjustments to reconcile net (loss) income to net cash provided by operating activities
Unrealized loss on derivatives	4,825	3,270
Depletion, depreciation and amortization	28,232	11,205
Accretion of asset retirement obligations	81	53
Full-cost ceiling impairment	21,230
Stock-based compensation expense	492	(363)
Deferred income tax provision		3,064
Changes in operating assets and liabilities
Accounts receivable	1,752	(8,456)
Lease and well equipment inventory	121
Prepaid expenses	(493)	(544)
Other assets	(172)	13
Accounts payable, accrued liabilities and other current liabilities	(10,788)	(8,563)
Royalties payable	1,165	1,341
Advances from joint interest owners	1,034
Income taxes payable	46
Other long-term liabilities	209	289
Net cash provided by operating activities	32,229	5,110
Investing activities
Oil and natural gas properties capital expenditures	(83,387)	(51,959)
Expenditures for other property and equipment	(1,374)	(1,413)
Purchases of certificates of deposit	(61)	(150)
Maturities of certificates of deposit	150	758
Net cash used in investing activities	(84,672)	(52,764)
Financing activities
Repayments of borrowings under Credit Agreement		(123,000)
Borrowings under Credit Agreement	55,000	25,000
Proceeds from issuance of common stock		146,510
Cost to issue equity		(11,330)
Proceeds from stock options exercised		2,660
Payment of dividends - Class B		(96)
Net cash provided by financing activities	55,000	39,744
Increase (decrease) in cash	2,557	(7,910)
Cash at beginning of period	2,095	10,284
Cash at end of period	$ 4,652	$ 2,374