Annual report pursuant to Section 13 and 15(d)

Derivative Financial Instruments And Hedging Activities (Outstanding Derivatives On Individual Contract Basis) (Details)

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Derivative Financial Instruments And Hedging Activities (Outstanding Derivatives On Individual Contract Basis) (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2011
Dec. 31, 2010
Derivative Financial Instruments And Hedging Activities [Line Items]    
Fair Value of Derivatives with Unrealized Gains $ 46,328 $ 18,568
Fair Value of Derivatives with Unrealized Losses 23,513 28,815
Designated As Hedging Instrument [Member]
   
Derivative Financial Instruments And Hedging Activities [Line Items]    
Fair Value of Derivatives with Unrealized Gains 45,071 18,389
Fair Value of Derivatives with Unrealized Losses 22,406 27,916
Dedesignated As Hedging Instrument [Member]
   
Derivative Financial Instruments And Hedging Activities [Line Items]    
Fair Value of Derivatives with Unrealized Gains 1,245 179
Fair Value of Derivatives with Unrealized Losses 930 899
Not Designated As Hedging Instrument [Member]
   
Derivative Financial Instruments And Hedging Activities [Line Items]    
Fair Value of Derivatives with Unrealized Gains 12  
Fair Value of Derivatives with Unrealized Losses $ 177