Condensed Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revenues
Oil and natural gas revenues	$ 81,868	$ 38,008	$ 199,367	$ 103,250
Realized gain on derivatives	(1,165)	3,371	(519)	11,147
Unrealized loss on derivatives	(9,327)	(12,993)	(6,626)	(1,149)
Total revenues	71,376	28,386	192,222	113,248
Expenses
Production taxes and marketing	6,559	2,822	15,107	7,605
Lease operating	8,569	6,491	29,608	17,511
Depletion, depreciation and amortization	26,127	21,680	74,593	52,799
Accretion of asset retirement obligations	86	59	248	170
Full-cost ceiling impairment	0	3,596	21,229	36,801
General and administrative	5,395	3,439	14,146	11,321
Total expenses	46,736	38,087	154,931	126,207
Operating (loss) income	24,640	(9,701)	37,291	(12,959)
Other income (expense)
Net loss on asset sales and inventory impairment	0	0	(192)	(60)
Interest expense	(2,038)	(144)	(4,919)	(453)
Interest and other income	66	55	181	157
Total other expense	(1,972)	(89)	(4,930)	(356)
Income (loss) before income taxes	22,668	(9,790)	32,361	(13,315)
Income tax provision (benefit)
Current	902	188	980	188
Deferred	1,661	(781)	1,661	(1,430)
Total income tax provision (benefit)	2,563	(593)	2,641	(1,242)
Net income (loss)	$ 20,105	$ (9,197)	$ 29,720	$ (12,073)
Basic
Basic (shares)	58,016	55,271	55,766	53,519
Diluted
Diluted (shares)	58,152	55,271	55,889	53,519
Class A
Basic
Basic (usd per share)	$ 0.35	$ (0.17)	$ 0.53	$ (0.23)
Diluted
Diluted (usd per share)	$ 0.35	$ (0.17)	$ 0.53	$ (0.23)
Basic
Basic (shares)	58,016	55,271	55,766	53,379
Diluted
Diluted (shares)	58,152	55,271	55,889	53,379
Class B
Basic
Basic (usd per share)	$ 0.00	$ 0.00	$ 0.00	$ (0.03)
Diluted
Diluted (usd per share)	$ 0.00	$ 0.00	$ 0.00	$ (0.03)
Basic
Basic (shares)	0	0	0	140
Diluted
Diluted (shares)	0	0	0	140