CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating Revenues
Oil and gas sales	$ 32,608	$ 34,682	$ 30,735	$ 30,819	$ 31,904	$ 31,361	$ 30,178	$ 28,354	$ 127,925	$ 121,797	$ 103,371
Transportation revenue									919
Total revenues									128,844	121,797	103,371
Operating Expenses
Lease operating expenses									36,779	33,072	30,637
Depreciation, depletion and amortization									44,806	47,172	30,517
Transportation expenses									311
General and administrative									15,389	19,844	14,819
Total operating expenses									97,285	100,088	75,973
Income from operations									31,559	21,709	27,398
Other income (expense)
Interest and other income									5,362	90	77
Interest expense									(2,995)	(3,311)	(3,188)
Gain (loss) on derivative financial instruments									(3,477)	(2,975)	(2,726)
Net other expense									(1,110)	(6,196)	(5,837)
Income before provision for income taxes									30,449	15,513	21,561
Deferred income tax expense (benefit)									64	(7)	(78)
Net income	3,713	14,658	9,185	2,829	4,042	2,408	5,259	3,811	30,385	15,520	21,639
Less dividends and accretion on preferred shares									10	10	10
Net income applicable to common stockholders	$ 3,710	$ 14,656	$ 9,183	$ 2,826	$ 4,040	$ 2,405	$ 5,257	$ 3,808	$ 30,375	$ 15,510	$ 21,629
Income per common share-Basic (in dollars per share)	$ 0.05	$ 0.20	$ 0.13	$ 0.04	$ 0.06	$ 0.03	$ 0.07	$ 0.05	$ 0.42	$ 0.22	$ 0.31
Income per common share-Diluted (in dollars per share)	$ 0.05	$ 0.20	$ 0.13	$ 0.04	$ 0.06	$ 0.03	$ 0.07	$ 0.05	$ 0.42	$ 0.22	$ 0.30
Weighted average common shares outstanding-Basic (in shares)									72,390,584	71,376,046	70,830,855
Weighted average common shares outstanding-Diluted (in shares)									72,546,209	72,096,672	72,047,488