Quarterly report pursuant to Section 13 or 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
Mar. 31, 2012
Dec. 31, 2011
Apr. 02, 2011
Derivative Financial Instruments And Hedging Activities [Line Items]      
Fair Value of Derivatives with Unrealized Gains $ 26,035 $ 46,328 $ 18,771
Fair Value of Derivatives with Unrealized Losses 14,933 23,513 55,469
Designated As Hedging Instrument [Member]
     
Derivative Financial Instruments And Hedging Activities [Line Items]      
Fair Value of Derivatives with Unrealized Gains 25,568 45,071 17,974
Fair Value of Derivatives with Unrealized Losses 13,598 22,406 55,116
Dedesignated As Hedging Instrument [Member]
     
Derivative Financial Instruments And Hedging Activities [Line Items]      
Fair Value of Derivatives with Unrealized Gains 335 1,245 797
Fair Value of Derivatives with Unrealized Losses 1,070 930 353
Not Designated As Hedging Instrument [Member]
     
Derivative Financial Instruments And Hedging Activities [Line Items]      
Fair Value of Derivatives with Unrealized Gains 132 12  
Fair Value of Derivatives with Unrealized Losses $ 265 $ 177