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           Interest Costs (Details) (USD $) 
        In Thousands  | 
        3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
| 
           Jun. 30, 2011 
         | 
        
           Jun. 30, 2010 
         | 
        
           Jun. 30, 2011 
         | 
        
           Jun. 30, 2010 
         | 
      |
| Interest Cost | ||||
| Interest costs charged to expense | $ 76,196 | $ 76,802 | $ 154,414 | $ 154,670 | 
| Interest costs capitalized | 8,068 | 16,253 | 15,318 | 30,430 | 
| Total interest costs incurred | 84,264 | 93,055 | 169,732 | 185,100 | 
| Interest Costs (Textuals) [Abstract] | ||||
| Non cash interest expense included in interest costs | $ 9,661 | $ 11,175 | $ 19,234 | $ 22,294 | 
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- Definition 
          Interest Cost. 
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- Definition 
          Interest Costs. 
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- Definition 
          The amount of interest that was capitalized during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          Total interest costs incurred during the period and either capitalized or charged against earnings. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          The cost of borrowed funds accounted for as interest that was charged against earnings during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          Interest paid other than in cash for example by issuing additional debt securities. As a noncash item, it is added to net income when calculating cash provided by or used in operations using the indirect method. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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