Derivatives And Risk Management (Derivative Instruments Summary) (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Derivatives, Fair Value [Line Items]
Asset	$ 59,134	$ 35,105
Liability	(143,462)	(99,530)
Net Asset (Liability)	(84,328)	(64,425)
Other Current Liabilities [Member] | Foreign Currency Exchange Contracts [Member]
Derivatives, Fair Value [Line Items]
Liability	(523)
Net Asset (Liability)	(523)
Other Current Liabilities [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Liability	(14,077)
Net Asset (Liability)	(14,077)
Other Current Assets [Member] | Foreign Currency Exchange Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset		116
Net Asset (Liability)		116
Other Property And Investments-Net [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset		127
Net Asset (Liability)		127
Other Non-Current Liabilities And Deferred Credits [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Liability	(148)	(53)
Net Asset (Liability)	(148)	(53)
Other Non-Current Liabilities And Deferred Credits [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset	20,643	1,386
Liability	(43,040)	(32,371)
Net Asset (Liability)	(22,397)	(30,985)
Current Utility Energy Commodity Derivative Assets [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset	1,478	6,293
Liability	(989)	(3,701)
Net Asset (Liability)	489	2,592
Non-Current Utility Energy Commodity Derivative Assets [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset	12,345	21,249
Liability	(6,750)	(5,988)
Net Asset (Liability)	5,595	15,261
Current Utility Energy Commodity Derivative Liabilities [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset	24,668	5,934
Liability	(77,935)	(57,417)
Net Asset (Liability)	$ (53,267)	$ (51,483)