| 
           Commitments And Contingencies (Narrative) (Details) (USD $) 
         | 
        3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
| 
           Jun. 30, 2011 
         | 
        
           Jun. 30, 2010 
         | 
        
           Jun. 30, 2011 
         | 
        
           Jun. 30, 2010 
         | 
      |
| Ground lease expense incurred | $ 102,000 | $ 127,000 | $ 203,000 | $ 286,000 | 
| 
           Property Lock-Ups [Member] 
         | 
        ||||
| Properties aggregate net book value | 132,800,000 | |||
| Expiration year | 2016 | |||
| Number of properties | 7 | 7 | ||
| 
           Property Lock-Ups Expired [Member] 
         | 
        ||||
| Properties aggregate net book value | 1,800,000,000 | |||
| Number of properties | 129 | 129 | ||
| 
           Harborside Plaza 4-A Agreement [Member] 
         | 
        ||||
| Project period (years) | 20 | |||
| Percentage of PILOT on project cost | 2.00% | |||
| Total project cost | 49,500,000 | |||
| Payments in lieu of property taxes (PILOT) | 247,000 | 275,000 | 495,000 | 550,000 | 
| 
           Harborside Plaza 5 Agreement [Member] 
         | 
        ||||
| Project period (years) | 20 | |||
| Percentage of PILOT on project cost | 2.00% | |||
| Total project cost | 170,900,000 | |||
| Payments in lieu of property taxes (PILOT) | $ 854,000 | $ 798,000 | $ 1,700,000 | $ 1,600,000 | 
| X | ||||||||||
| 
             
- Definition 
          Estimated Cost Of Project 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Rent expense for each period for which an income statement is presented for minimum lease payments, contingent rentals, and sublease rentals. 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Payments in Lieu of Property Tax As Percentage of Total Project Cost 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Payments In Lieu Of Property Taxes 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Project Term 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Properties Restriction For Sale Expiration Period 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Property Net Book Value 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          The number of real estate properties owned as of the balance sheet date. 
  |