Quarterly report pursuant to Section 13 or 15(d)

Investments In Unconsolidated Joint Ventures (Boston-Downtown Crossing) (Narrative) (Details)

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Investments In Unconsolidated Joint Ventures (Boston-Downtown Crossing) (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
0 Months Ended
Apr. 23, 2013
Mar. 31, 2013
sqft
Boston Downtown Crossing [Member]
   
Schedule of Equity Method Investments [Line Items]    
Area of property (in square feet)   1,200,000
Percentage of interest in venture   15.00%
Venture sale of real estate $ 45.0  
Share of gain on sale of real estate $ 13.5  
Minimum [Member]
   
Schedule of Equity Method Investments [Line Items]    
Percentage of interest in venture   7.50%
Maximum [Member]
   
Schedule of Equity Method Investments [Line Items]    
Percentage of interest in venture   80.00%