Condensed Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Current assets
Cash	$ 4,652	$ 2,095
Certificates of deposit	141	230
Accounts receivable
Oil and natural gas revenues	22,232	24,422
Joint interest billings	4,862	4,118
Other	668	974
Derivative instruments	1,142	4,378
Deferred income taxes	1,008
Lease and well equipment inventory	966	877
Prepaid expenses	1,597	1,103
Total current assets	37,268	38,197
Oil and natural gas properties, full-cost method
Evaluated	830,254	763,527
Unproved and unevaluated	151,161	149,675
Other property and equipment	27,596	27,258
Less accumulated depletion, depreciation and amortization	(398,832)	(349,370)
Net property and equipment	610,179	591,090
Other assets
Derivative instruments	1,143	771
Deferred income taxes		411
Other assets	1,732	1,560
Total other assets	2,875	2,742
Total assets	650,322	632,029
Current liabilities
Accounts payable	19,675	28,120
Accrued liabilities	40,214	59,179
Royalties payable	7,706	6,541
Derivative instruments	2,215	670
Advances from joint interest owners	2,549	1,515
Income taxes payable	46
Deferred income taxes		411
Other current liabilities	78	56
Total current liabilities	72,483	96,492
Long-term liabilities
Borrowings under Credit Agreement	205,000	150,000
Asset retirement obligations	5,746	5,109
Derivative instruments	416
Deferred income taxes	1,008
Other long-term liabilities	1,564	1,324
Total long-term liabilities	213,734	156,433
Commitments and contingencies (Note 9)
Shareholders' equity
Common stock - $0.01 par value, 80,000,000 shares authorized; 57,104,489 and 56,778,718 shares issued; and 55,842,938 and 55,577,667 shares outstanding, respectively	571	568
Additional paid-in capital	404,814	404,311
Retained deficit	(30,515)	(15,010)
Treasury stock, at cost, 1,261,551 and 1,201,051 shares, respectively	(10,765)	(10,765)
Total shareholders' equity	364,105	379,104
Total liabilities and shareholders' equity	$ 650,322	$ 632,029