Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Current assets
Cash	$ 2,095	$ 10,284
Certificates of deposit	230	1,335
Accounts receivable
Oil and natural gas revenues	24,422	9,237
Joint interest billings	4,118	2,488
Other	974	1,447
Derivative instruments	4,378	8,989
Lease and well equipment inventory	877	1,343
Prepaid expenses	1,103	1,153
Total current assets	38,197	36,276
Oil and natural gas properties, full-cost method
Evaluated	763,527	423,945
Unproved and unevaluated	149,675	162,598
Other property and equipment	27,258	18,764
Less accumulated depletion, depreciation and amortization	(349,370)	(205,442)
Net property and equipment	591,090	399,865
Other assets
Derivative instruments	771	847
Deferred income taxes	411	1,594
Other assets	1,560	887
Total other assets	2,742	3,328
Total assets	632,029	439,469
Current liabilities
Accounts payable	28,120	18,841
Accrued liabilities	59,179	25,439
Royalties payable	6,541	1,855
Borrowings under Credit Agreement		25,000
Derivative instruments	670	171
Advances from joint interest owners	1,515
Deferred income taxes	411	3,024
Dividends payable - Class B		69
Other current liabilities	56	177
Total current liabilities	96,492	74,576
Long-term liabilities
Borrowings under Credit Agreement	150,000	88,000
Asset retirement obligations	5,109	3,935
Derivative instruments		383
Deferred income taxes	40,845	29,100
Other long-term liabilities	1,324	1,060
Total long-term liabilities	156,433	93,378
Commitments and contingencies (Note 13)
Shareholders' equity
Additional paid-in capital	404,311	263,562
Retained (deficit) earnings	(15,010)	18,279
Treasury stock, at cost, 1,201,051 and 1,179,175 shares, respectively	(10,765)	(10,765)
Total shareholders' equity	379,104	271,515
Total liabilities and shareholders' equity	632,029	439,469
Class A
Shareholders' equity
Common stock	568	429
Class B
Shareholders' equity
Common stock		$ 10