Annual report pursuant to Section 13 and 15(d)

Recent Transactions (Other Investments In 2016) (Narrative) (Details)

v3.8.0.1
Recent Transactions (Other Investments In 2016) (Narrative) (Details)
$ in Thousands
12 Months Ended
Apr. 26, 2016
USD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
ft²
item
Dec. 31, 2015
USD ($)
Real Estate Properties [Line Items]        
Purchase price of property | $   $ 90,068 $ 121,582 $ 94,073
Weehawken, New Jersey [Member]        
Real Estate Properties [Line Items]        
Purchase price of property | $ $ 36,400      
Port Imperial 4/5 Garage And Retail [Member] | Projects Under Development And Developable Land [Member]        
Real Estate Properties [Line Items]        
Number of units | item     1,100  
Area of property (in square feet) | ft²     290,000  
Percentage of interest in venture     52.50%  
Port Imperial South 11 [Member] | Weehawken, New Jersey [Member]        
Real Estate Properties [Line Items]        
Number of units | item     295