| 
           Investments In Unconsolidated Joint Ventures (Stamford SM LLC) (Details) (USD $) 
        In Millions, unless otherwise specified  | 
        0 Months Ended | 9 Months Ended | ||||
|---|---|---|---|---|---|---|
| 
           Feb. 17, 2012
 
          Class A Portfolio In Stamford, Connecticut [Member]
 
          sqft 
         | 
        
           Feb. 17, 2012
 
          Class A Office Space [Member]
 
          property
 
          sqft 
         | 
        
           Feb. 17, 2012
 
          Residential Space [Member]
 
          property
 
          sqft 
         | 
        
           Sep. 30, 2012
 
          Stamford SM LLC [Member] 
         | 
        
           Sep. 30, 2012
 
          Mezz Loan [Member] 
         | 
        
           Feb. 17, 2012
 
          Mezz Loan [Member] 
         | 
      |
| Schedule of Equity Method Investments [Line Items] | ||||||
| Area of office property, square feet | 1,700,000 | 1,670,000 | 70,500 | |||
| Venture property acquisition cost | $ 40 | |||||
| Mortgage loan face amount | 50.0 | |||||
| Number of properties | 7 | |||||
| Number of rental units | 106 | |||||
| Mortgage loan carrying amount | 41.6 | |||||
| Threshold of which excess proceeds are paid to another party | $ 47 | |||||
| Spread over LIBOR | 3.25% | |||||
| Mortgage loan, extension period | 1 year | |||||
| Percentage of interest in venture | 80.00% | |||||
| Third party ownership percentage | 20.00% | |||||
| Mortgage loan scheduled to mature | Aug. 01, 2013 | |||||
| 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 equally in decision-making on all major decisions involving the operations of the joint venture. | |||||
| X | ||||||||||
| 
             
- Definition 
          Area of Property in Square foot No definition available. 
  | 
        
| X | ||||||||||
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- Definition 
          Holding And Distribution Pattern Under Operating Agreement No definition available. 
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| X | ||||||||||
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- Definition 
          Mortgage Loan Extension Period No definition available. 
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| X | ||||||||||
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- Definition 
          Third Party Ownership Percent No definition available. 
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| X | ||||||||||
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- Definition 
          Threshold Of Which Excess Proceeds Are Paid To Third Party No definition available. 
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| X | ||||||||||
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- Definition 
          Cost of property acquired by the venture. No definition available. 
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| X | ||||||||||
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- Definition 
          The percentage points added to the reference rate to compute the variable rate on the debt instrument. No definition available. 
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| X | ||||||||||
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- Definition 
          The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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| X | ||||||||||
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- Definition 
          Stated maturity date of the mortgage loan receivable on real estate, in CCYY-MM-DD format. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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| X | ||||||||||
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- Definition 
          The carrying amount of the outstanding balance due under the mortgage loan. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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| X | ||||||||||
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- Definition 
          Amount of the contractual principal due at the origination of the mortgage loan (face amount). Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
        
| X | ||||||||||
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- Definition 
          The number of real estate properties owned as of the balance sheet date. No definition available. 
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| X | ||||||||||
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- Definition 
          The number of units in a real estate property owned as of the balance sheet date. No definition available. 
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| X | ||||||||||
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- Details 
          
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