Supplemental Oil And Natural Gas Disclosures (Unaudited) (Details Textuals) (USD $)	12 Months Ended
	Dec. 31, 2012 bbl	Dec. 31, 2011	Dec. 31, 2010 bbl
Property, Plant and Equipment [Line Items]
Proved Developed and Undeveloped Reserves, Extensions, Discoveries, and Additions	114.2
Decrease Due to Sales of Minerals in Place	123.9
Cash paid for interest, capitalized	$ 77,432,000	$ 61,586,000	$ 66,815,000
Costs incurred include new asset retirement obligations established and changes to asset retirement cost estimates or abandonment dates obligations resulting from revisions in cost estimates or abandonment dates	38,800,000	24,200,000	45,100,000
Capitalized general and administrative costs	49,200,000	35,000,000	20,100,000
Improved recovery			39.4
Oil and Gas Properties [Member]
Property, Plant and Equipment [Line Items]
Cash paid for interest, capitalized	$ 36,500,000	$ 44,900,000	$ 32,600,000
Increase In Proved Reserves Related To Hastings And Oyster Bayou [Member]
Property, Plant and Equipment [Line Items]
Proved Developed and Undeveloped Reserves, Extensions, Discoveries, and Additions	69.5
Increase In Proved Reserves Related To Thompson Webster And Hartzog Draw [Member]
Property, Plant and Equipment [Line Items]
Proved Developed and Undeveloped Reserves, Purchases of Minerals in Place	25.9
Increase In Proved Reserves Related To Bakken [Member]
Property, Plant and Equipment [Line Items]
Proved Developed and Undeveloped Reserves, Extensions, Discoveries, and Additions	11.5