Annual report pursuant to Section 13 and 15(d)

Noncontrolling Interests In Subsidiaries (Narrative) (Details)

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Noncontrolling Interests In Subsidiaries (Narrative) (Details) (USD $)
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Noncontrolling Interest [Line Items]      
Preferred stock issued   $ 25,000,000  
Increase in noncontrolling interest (107,000) (321,000) 3,186,000
Rebalance of ownership percentage 9,400,000    
Percentage of noncontrolling interest 12.20% 14.00%  
Square footage of office buildings 860,246    
Excess net cash flow remaining after the distribution to the Company 50.00%    
Internal rate of return 10.00%    
Series C Preferred Stock [Member]
     
Noncontrolling Interest [Line Items]      
Preferred unit in operating partnership 25,000,000    
Series C Cumulative Redeemable Perpetual Preferred Stock [Member]
     
Noncontrolling Interest [Line Items]      
Preferred stock issued $ 25,000,000