| 
           Tenant Leases (Future Minimum Rentals To Be Received Under Non-Cancelable Operating Leases) (Details) (USD $) 
        In Thousands  | 
        6 Months Ended | 
|---|---|
| 
           Jun. 30, 2011 
         | 
      |
| Tenant Leases | |
| July 1 through December 31, 2011 | $ 296,893 | 
| 2012 | 565,575 | 
| 2013 | 493,813 | 
| 2014 | 428,475 | 
| 2015 | 358,208 | 
| 2016 and thereafter | 1,372,781 | 
| Total | $ 3,515,745 | 
| Operating leases with various expiration dates through year | 2033 | 
| X | ||||||||||
| 
             
- Definition 
          Tenant Leases [Abstract] 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          The date upon which a lease or a group of leases is set to expire. 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Future minimum rental payments in aggregate as of the balance sheet date under operating leases. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Future rental payments receivable within one year of the balance sheet date under an operating lease. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Future rental payments receivable within the fifth year from the balance sheet date under an operating lease. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Future rental payments receivable within the fourth year from the balance sheet date under an operating lease. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Future rental payments receivable within the third year from the balance sheet date under an operating lease. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Future rental payments receivable within the second year from the balance sheet date under an operating lease. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Future minimum lease payments receivable under operating leases for periods greater than five years following the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  |