Annual report pursuant to Section 13 and 15(d)

Recent Transactions (Acquisitions) (Narrative) (Details)

v3.3.1.900
Recent Transactions (Acquisitions) (Narrative) (Details)
$ in Thousands
12 Months Ended
Jan. 05, 2016
USD ($)
item
Dec. 23, 2015
USD ($)
ft²
Nov. 12, 2015
USD ($)
ft²
Dec. 02, 2014
USD ($)
Aug. 15, 2014
USD ($)
property
Apr. 10, 2014
USD ($)
item
Dec. 31, 2015
USD ($)
item
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Real Estate Properties [Line Items]                  
Purchase price of property             $ 94,073 $ 91,813 $ 89,869
Acquisition and other investment fundings handled by intermediary               $ 44,400  
Minimum [Member]                  
Real Estate Properties [Line Items]                  
Percentage of interest in venture             7.50%    
Maximum [Member]                  
Real Estate Properties [Line Items]                  
Percentage of interest in venture             85.00%    
Multi-Family Properties [Member]                  
Real Estate Properties [Line Items]                  
Number of units | item             5,644    
Conshohocken, Pennsylvania [Member]                  
Real Estate Properties [Line Items]                  
Purchase price of property       $ 15,300          
Andover Place [Member]                  
Real Estate Properties [Line Items]                  
Number of units | item           220      
Purchase price of property           $ 37,700      
Overlook Ridge Properties [Member]                  
Real Estate Properties [Line Items]                  
Purchase price of property         $ 16,600        
Overlook Ridge Properties [Member] | Consolidated Land [Member]                  
Real Estate Properties [Line Items]                  
Loans assumed         $ 23,000        
Percentage of interest in developable land         100.00%        
Overlook Ridge Properties [Member] | Consolidated Land [Member] | Minimum [Member]                  
Real Estate Properties [Line Items]                  
Spread over LIBOR         2.50%        
Overlook Ridge Properties [Member] | Consolidated Land [Member] | Maximum [Member]                  
Real Estate Properties [Line Items]                  
Spread over LIBOR         3.50%        
Overlook Ridge Properties [Member] | Multi-Family Properties [Member]                  
Real Estate Properties [Line Items]                  
Percentage of additional interest acquired         25.00%        
Indirect ownership interest         50.00%        
Number of properties in which additional interest was acquired during period | property         2        
Curtis Center [Member]                  
Real Estate Properties [Line Items]                  
Percentage of interest in venture               50.00%  
Acquisition and other investment fundings handled by intermediary               $ 40,100  
Overlook Ridge Apartments Investors, L.L.C. [Member] | Subsequent Event [Member]                  
Real Estate Properties [Line Items]                  
Percentage of interest in venture 50.00%                
Number of units | item 371                
Purchase price of property $ 39,800                
Parsippany [Member]                  
Real Estate Properties [Line Items]                  
Area of property (in square feet) | ft²   147,241              
Purchase price of property   $ 10,300              
Edison [Member]                  
Real Estate Properties [Line Items]                  
Area of property (in square feet) | ft²     196,128            
Purchase price of property     $ 53,100