Oil And Gas Properties (Narrative) (Details) (USD $)	0 Months Ended	1 Months Ended	12 Months Ended
	Feb. 06, 2013	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011 item	Dec. 31, 2010 item
Oil And Gas Properties [Line Items]
Supplies		$ 1,677,000	$ 2,480,000	$ 1,677,000
Inventory Write-down				2,100,000
Pipe Inventory Sold		4,600,000		4,600,000
Non-hedge loss on commodity derivative contracts			(10,507,000)
Number of oil and gas properties impaired				11	21
Proceeds from Divestiture of Businesses	620,000,000
Gas Balancing Asset (Liability)			1,000,000
Dry hole expense			(55,000)	(70,000)	(424,000)
Oil and gas property impairments			138,600,000	90,900,000	176,700,000
Impairment of unproved properties			833,000	8,334,000	6,394,000
Capitalized exploration cost			8,200,000
Royalty Payments To US Government			78,100,000	85,400,000	37,200,000
Asset retirement obligation		227,090,000	200,978,000	227,090,000	222,653,000
AssetRetirementObligationRevisionOfEstimate			62,834,000	22,345,000
Number Of Oil And Gas Properties Impaired				11	21
Net interest expense			48,160,000	70,181,000	65,589,000
Proceeds from Sale of Other Assets		2,500,000
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax			6,800,000
Energy Resource Technology GOM, Inc [Member]
Oil And Gas Properties [Line Items]
Net interest expense			27,700,000	25,200,000	19,700,000
Camelot Field [Member]
Oil And Gas Properties [Line Items]
Oil and gas property impairments					4,100,000
Asset retirement obligation		27,300,000		27,300,000
Abandonment Expense			15,500,000
Non Producing Oil And Gas Properties [Member]
Oil And Gas Properties [Line Items]
AssetRetirementObligationRevisionOfEstimate			12,400,000	22,500,000
Gulf Of Mexico Oil And Gas Properties [Member]
Oil And Gas Properties [Line Items]
Oil and gas property impairments					172,600,000
Non-Domestic Oil And Gas Property [Member]
Oil And Gas Properties [Line Items]
Oil and gas property impairments					4,100,000
Segment, Discontinued Operations [Member]
Oil And Gas Properties [Line Items]
Supplies		16,400,000	11,900,000	16,400,000
Restricted cash		33,700,000	28,400,000	33,700,000
Other Assets Current Gas Imbalances			4,000,000
Gas Balancing Payable, Current			$ 3,000,000