Investments In Unconsolidated Joint Ventures (Stamford SM LLC) (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2012
sqft
Class A Portfolio In Stamford, Connecticut [Member]
  
Schedule of Equity Method Investments [Line Items]  
Area of office property, square feet 1,700,000
Venture property acquisition cost $ 40
Class A Office Space [Member]
  
Schedule of Equity Method Investments [Line Items]  
Area of office property, square feet 1,670,000
Number of properties 7
Residential Space [Member]
  
Schedule of Equity Method Investments [Line Items]  
Area of office property, square feet 70,500
Number of rental units 106
Stamford SM LLC [Member]
  
Schedule of Equity Method Investments [Line Items]  
Percentage of interest in venture 80.00%
Third party ownership percentage 20.00%
Holding and distribution pattern under operating agreement

The operating agreement of Stamford SM provides, among other things, distributions of net available cash in accordance with its members' respective ownership percentages.  The Company owns an 80 percent interest in the venture.  The Company and the 20 percent member share decision-making regarding all major decisions involving the operations of the joint venture.
Mezz Loan [Member]
  
Schedule of Equity Method Investments [Line Items]  
Mortgage loan face amount 50.0
Mortgage loan carrying amount 40.3
Spread over LIBOR 325
Threshold of which excess proceeds are paid to another party $ 47.0
Mortgage loan scheduled to mature Aug. 01, 2012
Number of extension options 2
Mortgage loan, extension period (in years) 1