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           Financial Instruments - Fair Value and Settlements of Derivatives (Details) (USD $) 
        In Thousands, unless otherwise specified  | 
        3 Months Ended | ||
|---|---|---|---|
| 
           Mar. 31, 2013 
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           Mar. 31, 2012 
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           Dec. 31, 2012 
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      |
| Derivative [Line Items] | |||
| Derivative, Collateral, Right to Reclaim Cash | $ 6,400 | $ 5,900 | |
| Derivative gain (loss) | (17,468) | (836) | |
| 
           Fuel Derivatives [Member] 
         | 
        |||
| Derivative [Line Items] | |||
| Derivative, Collateral, Right to Reclaim Cash | 0 | 0 | |
| Derivative gain (loss) | 515 | (836) | |
| 
           LNG Inventory Derivatives [Member] 
         | 
        |||
| Derivative [Line Items] | |||
| Derivative, Collateral, Right to Reclaim Cash | 0 | 0 | |
| Derivative gain (loss) | $ (524) | $ 1,859 | |
| X | ||||||||||
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- Definition 
          The amount of the right to reclaim cash collateral under master netting arrangements that have not been offset against net derivative instrument positions. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Details 
          
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- Definition 
          Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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