Supplemental Oil and Natural Gas Disclosures (Unaudited) (Details 4) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2011	Jun. 30, 2012	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summarizes the changes in the standardized measure of discounted future net cash flows relating to proved oil and natural gas reserves
Balance, beginning of period	$ 111,077	$ 215,473	$ 215,473	$ 215,473	$ 111,077	$ 65,061
Net change in sales and transfer prices and in production (lifting) costs related to future production				(60,892)	53,903	7,632
Changes in estimated future development costs				16,937	(64,958)	(36,821)
Sales and transfers of oil and natural gas produced during the period				(116,142)	(53,478)	(26,776)
Net change due to extensions and discoveries				358,159	182,282	94,265
Net change due to revisions in estimates of reserves quantities				(56,850)	(653)	1,676
Previously estimated development costs incurred during the period				9,750	1,023	7,125
Accretion of Discount				24,873	11,987	7,036
Other				(290)	(1,335)	1,035
Net change in income taxes	12,700	11,900	1,300	3,618,000	(24,375)	(9,156)
Standardized measure of discounted future net cash flows				$ 394,636	$ 215,473	$ 111,077