Condensed Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Current assets
Cash and cash equivalents	$ 9,432	$ 10,284
Certificates of deposit	266	1,335
Accounts receivable
Oil and natural gas revenues	11,898	9,237
Joint interest billings	2,378	2,488
Other	1,656	1,447
Derivative instruments	16,033	8,989
Lease and well equipment inventory	1,381	1,343
Prepaid expenses	1,538	1,153
Total current assets	44,582	36,276
Oil and natural gas properties, full-cost method
Evaluated	564,026	423,945
Unproved and unevaluated	166,230	162,598
Other property and equipment	22,102	18,764
Less accumulated depletion, depreciation and amortization	(269,766)	(205,442)
Net property and equipment	482,592	399,865
Other assets
Derivative instruments	5,093	847
Deferred income taxes	4,594	1,594
Other assets	828	887
Total other assets	10,515	3,328
Total assets	537,689	439,469
Current liabilities
Accounts payable	16,874	18,841
Accrued liabilities	36,259	25,439
Royalties payable	5,497	1,855
Borrowings under Credit Agreement		25,000
Derivative instruments		171
Deferred income taxes	5,376	3,024
Dividends payable - Class B		69
Other current liabilities	56	177
Total current liabilities	64,062	74,576
Long-term liabilities
Borrowings under Credit Agreement	60,000	88,000
Asset retirement obligations	4,363	3,935
Derivative instruments		383
Other long-term liabilities	1,487	1,060
Total long-term liabilities	65,850	93,378
Commitments and contingencies (Note 10)
Shareholders' equity
Additional paid-in capital	402,622	263,562
Retained earnings	15,376	18,279
Treasury stock, at cost, 1,189,175 shares	(10,787)	(10,765)
Total shareholders' equity	407,777	271,515
Total liabilities and shareholders' equity	537,689	439,469
Class A
Shareholders' equity
Common stock	566	429
Class B
Shareholders' equity
Common stock		$ 10