| 
           Properties, net (Details 2) (USD $) 
        In Thousands  | 
        
           Jun. 30, 2011 
         | 
        
           Dec. 31, 2010 
         | 
      
|---|---|---|
| Properties | ||
| Properties under construction or development | $ 656,321 | $ 642,682 | 
| 
           Projects under construction or development | Land, development 
         | 
        ||
| Properties | ||
| Properties under construction or development | 248,647 | 256,487 | 
| 
           Projects under construction or development | Construction in progress, excluding land 
         | 
        ||
| Properties | ||
| Properties under construction or development | $ 407,674 | $ 386,195 | 
| X | ||||||||||
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- Definition 
          The current amount of expenditures for a real estate project that has not yet been completed. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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| X | ||||||||||
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- Definition 
          Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. 
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