Acquisitions and Divestitures (Details Textuals) (USD $)	3 Months Ended	6 Months Ended						1 Months Ended			3 Months Ended
	Jun. 30, 2012	Jun. 30, 2012	Jun. 30, 2011	Jun. 01, 2012	Oct. 31, 2010	Jun. 30, 2012 Petro Harvester [Member]	Mar. 31, 2012 Petro Harvester [Member]	Feb. 29, 2012 Petro Harvester [Member] Petro Harvester Gulf Coast Holdings LLC [Member]	Aug. 31, 2011 Riley Ridge Phase 2 [Member]	Jun. 01, 2012 Thompson Field [Member]	Jun. 30, 2012 Paradox Basin [Member]
Acquisitions and Divestitures (Textuals) [Abstract]
Working interest in business acquisition					42.50%				57.50%
Ownership Interest					42.50%				57.50%
Net proceeds from sales of oil and natural gas properties and equipment		$ 32,302,000	$ 18,432,000					$ 141,800,000			$ 68,500,000
Deferred Riley Ridge acquisition consideration									15,000,000
Anticipated Proceeds From Sale Of Oil And Natural Gas Properties								155,000,000			75,000,000
Business Acquisition, Cost of Acquired Entity, Purchase Price				366,178,000					214,800,000
Effective Date Of Transaction							Dec. 01, 2011			Jun. 01, 2012	Jan. 01, 2012
Net working interest acquired in purchase of oil and natural gas properties										nearly 100%
Net revenue interest acquired in purchase of oil and natural gas properties										84.70%
Net Revenue Interest Retained By Seller										5.00%
Oil Production Threshold										3,000
Business Acquisition Goodwill Acquired				127,229,000
Proceeds used in a like-kind exchange	212,500,000
Operating Revenues Net of Capital and Lease Operating Expense Between Effective Date and Closing Date of Sale Transaction						13,500,000
Business Acquisition, Purchase Price Allocation, Goodwill, Expected Tax Deductible Amount	$ 127,200,000	$ 127,200,000