Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating activities
Net (loss) income	$ (33,261)	$ (10,309)	$ 6,377
Adjustments to reconcile net (loss) income to net cash provided by operating activities
Unrealized loss (gain) on derivatives	4,802	(5,138)	(3,139)
Depletion, depreciation and amortization	80,454	31,754	15,596
Accretion of asset retirement obligations	256	209	155
Full-cost ceiling impairment	63,475	35,673	0
Stock option and grant expense	(589)	2,362	824
Restricted stock grants	729	44	74
Deferred income tax (benefit) provision	(1,430)	(5,475)	4,932
Loss on asset sales and inventory impairment	485	154	224
Changes in operating assets and liabilities
Accounts receivable	(16,342)	(1,523)	(386)
Lease and well equipment inventory	50	22	(8)
Prepaid expenses	50	650	(580)
Other assets	(673)	(814)	33
Accounts payable, accrued liabilities and other current liabilities	19,740	13,497	2,488
Royalties payable	4,685	873	309
Advances from joint interest owners	1,515	(723)	273
Other long-term liabilities	282	613	101
Net cash provided by operating activities	124,228	61,868	27,273
Investing activities
Oil and natural gas properties capital expenditures	(300,689)	(156,431)	(159,050)
Expenditures for other property and equipment	(7,332)	(4,671)	(1,610)
Purchases of certificates of deposit	(496)	(4,298)	(3,739)
Sales of certificates of deposit.	1,601	5,312	17,065
Net cash used in investing activities	(306,916)	(160,088)	(147,334)
Financing activities
Repayments of borrowings under Credit Agreement	(123,000)	(103,000)
Borrowings under Credit Agreement	160,000	191,000	25,000
Proceeds from issuance of common stock	146,510	592	20,652
Swing sale profit contribution	24
Cost to issue equity	(11,599)	(1,710)	(172)
Proceeds from stock options exercised	2,660	837	1,978
Payment of dividends - Class B	(96)	(275)	(275)
Purchases of treasury stock			(10,292)
Net cash provided by financing activities	174,499	87,444	36,891
Decrease in cash and cash equivalents	(8,189)	(10,776)	(83,170)
Cash and cash equivalents at beginning of year	10,284	21,060	104,230
Cash and cash equivalents at end of year	$ 2,095	$ 10,284	$ 21,060