Supplemental Oil and Natural Gas Disclosures (Unaudited) (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary of results of operations from oil and gas producing activities, excluding corporate overhead and interest costs
Oil and natural gas revenues	$ 52,748	$ 38,008	$ 36,078	$ 29,164	$ 14,991	$ 17,447	$ 20,864	$ 13,698	$ 155,998	$ 67,000	$ 34,042
Production taxes and marketing expenses									11,672	6,278	1,982
Lease operating expenses									28,184	7,244	5,284
Depletion, depreciation and amortization									79,592	31,619	15,423
Accretion of asset retirement obligations									1,195	488	862
Full-cost ceiling impairment									63,475	35,673	0
Net operating (loss) income									(27,181)	(14,023)	11,198
Income tax (benefit) provision									(9,595)	(5,019)	3,983
Results of oil and natural gas operations									$ (17,586)	$ (9,004)	$ 7,215
Depletion, depreciation and amortization per BOE									24.16	12.29	10.76