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           Interest Costs (Details) (USD $) 
        In Thousands, unless otherwise specified  | 
        3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
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           Sep. 30, 2014 
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           Sep. 30, 2013 
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           Sep. 30, 2014 
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           Sep. 30, 2013 
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| Interest Cost | ||||
| Interest costs charged to expense | $ 75,416 | $ 54,629 | $ 197,029 | $ 150,531 | 
| Interest costs capitalized | 70 | 7,915 | 480 | 23,923 | 
| Total interest costs incurred | 75,486 | 62,544 | 197,509 | 174,454 | 
| Interest Costs (Textual) [Abstract] | ||||
| Non cash interest expense included in interest costs | $ 5,736 | $ 5,574 | $ 16,515 | $ 16,506 | 
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- Definition 
          Amount of interest costs capitalized disclosed as an adjusting item to interest costs incurred. No definition available. 
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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 
          Amount of the cost of borrowed funds accounted for as interest expense. 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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