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Acquisitions and Divestitures (Details Textuals) (USD $)	3 Months Ended		6 Months Ended	9 Months Ended					1 Months Ended						1 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010	Mar. 31, 2010	Oct. 15, 2010 Riley Ridge [Member] Acres	May 31, 2010 Southern Assets [Member]	Aug. 31, 2010 Cleveland Sand Play [Member]	Aug. 01, 2011 Riley Ridge Phase 2 [Member]	Aug. 01, 2011 Additional Acres Surrounding Riley Ridge [Member]	Aug. 01, 2011 Riley Ridge Gas Plant [Member]	Oct. 15, 2010 Riley Ridge Gas Plant [Member]	Mar. 31, 2010 Genesis Energy LP [Member]	Feb. 28, 2010 Genesis Energy LLC [Member]
Acquisitions and Divestitures (Textuals) [Abstract]
Value of Encore Merger							$ 4,800,000,000
Revenues recognized from current period acquisitions		174,300,000	435,200,000
Transaction and other costs	0	11,470,000		4,377,000	79,253,000
Working interest in business acquisition								42.50%			57.50%	33.00%	57.50%	42.50%
Acreage adjacent to Riley Ridge								28,000
Business Acquisition, Percentage of CO2 rights in additional 28,000 acres								33.00%
Net Field Operating Income		114,100,000	294,800,000
Net proceeds from sale of interest in Genesis															79,000,000	84,000,000
Pre tax gain on sale of interest in Genesis	0	(3,000)		0	101,537,000
Gain on sale of interest in Genesis after tax					63,000,000
Net proceeds from sales of oil and natural gas properties and equipment				47,598,000	909,986,000				892,100,000	32,100,000
Contingent payment to be paid at the time the property's gas processing facility is operational and meets specific performance conditions	$ 15,000,000			$ 15,000,000		$ 0					$ 15,000,000