Annual report pursuant to Section 13 and 15(d)

Interest Costs (Details)

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Interest Costs (Details) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Interest Cost      
Interest costs charged to expense $ 304,938 $ 295,643 $ 315,668
Interest costs capitalized 33,522 63,880 61,201
Total interest costs incurred 338,460 359,523 376,869
Interest Costs (Textual) [Abstract]      
Non cash interest expense included in interest costs $ 39,515 $ 42,841 $ 43,066