Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Operating activities
Net (loss) income	$ (9,615)	$ 2,875
Adjustments to reconcile net (loss) income to net cash provided by operating activities
Unrealized loss on derivatives	(2,701)	(11,844)
Depletion, depreciation and amortization	48,466	31,119
Accretion of asset retirement obligations	161	111
Full-cost ceiling impairment	21,229	33,205
Stock-based compensation expense	(1,524)	172
Deferred income tax provision	0	(649)
Net loss on asset sales and inventory impairment	192	60
Changes in operating assets and liabilities
Accounts receivable	1,763	(2,761)
Lease and well equipment inventory	280	(98)
Prepaid expenses	(215)	(385)
Other assets	(117)	59
Accounts payable, accrued liabilities and other current liabilities	4,615	1,687
Royalties payable	206	(3,642)
Advances from joint interest owners	(1,515)	0
Income taxes payable	78	0
Other long-term liabilities	743	427
Net cash provided by operating activities	83,912	51,526
Investing activities
Oil and natural gas properties capital expenditures	(173,989)	(134,425)
Expenditures for other property and equipment	(2,081)	(3,521)
Purchases of certificates of deposit	(61)	(266)
Maturities of certificates of deposit	230	1,335
Net cash used in investing activities	(175,901)	(136,877)
Financing activities
Repayments of borrowings under Credit Agreement	0	(123,000)
Borrowings under Credit Agreement	95,000	70,000
Proceeds from issuance of common stock	0	146,510
Swing Sale Profit	0	24
Cost to issue equity	0	(11,599)
Proceeds from stock options exercised	0	2,660
Taxes paid related to net share settlement of stock-based compensation	(1)	0
Payment of dividends - Class B	0	(96)
Net cash provided by financing activities	94,999	84,499
Increase (decrease) in cash	3,010	(852)
Cash at beginning of period	2,095	10,284
Cash at end of period	$ 5,105	$ 9,432