Commitments And Contingencies (Other) (Narrative) (Details) (USD $)
3 Months Ended 0 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Aug. 01, 2014
Apr. 01, 2015
Dec. 31, 2014
Commitments And Contingencies [Line Items]          
Amount outstanding $ 42,000,000       $ 0
Investment in unconsolidated joint ventures 20,880,000 1,889,000      
Development of rental property 12,519,000 7,357,000      
Purchase price of property 19,658,000 14,600,000      
Eastchester Project [Member]          
Commitments And Contingencies [Line Items]          
Percentage of interest in venture 76.25%        
Number of units 108        
Project costs incurred to date 15,400,000        
Amount of project costs funded by members 20,900,000        
Total project costs 50,000,000        
Property Lock-Ups [Member]          
Commitments And Contingencies [Line Items]          
Number of properties 7        
Properties aggregate net book value 124,600,000        
Expiration year 2016        
Property Lock-Ups Expired [Member]          
Commitments And Contingencies [Line Items]          
Number of properties 110        
Properties aggregate net book value 1,300,000,000        
Harborside Unit A Urban Renewal, LLC [Member]          
Commitments And Contingencies [Line Items]          
Percentage of interest in venture 85.00% [1]        
Development costs 88,800,000        
Number of units 763        
Maximum borrowing capacity 192,000,000        
Amount outstanding 0        
Interest rate 5.197% [2]   5.197%    
Harborside Unit A Urban Renewal, LLC [Member] | Harborside Residential Project [Member]          
Commitments And Contingencies [Line Items]          
Total project costs 320,000,000        
Harborside Unit A Urban Renewal, LLC [Member] | Construction Loan [Member]          
Commitments And Contingencies [Line Items]          
Maximum borrowing capacity 192,000,000        
Mortgage loan, maturity date     Aug. 01, 2029    
Harborside Unit A Urban Renewal, LLC [Member] | Parent Company [Member]          
Commitments And Contingencies [Line Items]          
Total project costs 42,200,000        
150 Main Street, L.L.C. [Member] | Construction Loan [Member] | Eastchester Project [Member]          
Commitments And Contingencies [Line Items]          
Maximum borrowing capacity 28,800,000        
Amount outstanding 2,000,000        
Wegmans Food Markets, Inc. [Member]          
Commitments And Contingencies [Line Items]          
Costs of the project incurred 9,300,000        
Delivery date to tenant 2016        
Area of property (in square feet) 140,000        
Wegmans Food Markets, Inc. [Member] | Scenario, Forecast [Member]          
Commitments And Contingencies [Line Items]          
Total project costs 25,300,000        
Multi-Family Properties [Member]          
Commitments And Contingencies [Line Items]          
Number of units 5,861        
Subsequent Event [Member] | City Square Project [Member]          
Commitments And Contingencies [Line Items]          
Number of units       370  
Total project costs       88,000,000  
Purchase price of property       3,100,000  
Contingent consideration       $ 1,250,000  
Minimum project start period       12 months  
[1] Company's effective ownership % represents the Company's entitlement to residual distributions after payments of priority returns, where applicable.
[2] The construction/permanent loan has a maximum borrowing amount of $192,000.