Recent Transactions (Schedule Of Properties Which Commenced Initial Operations) (Details)
$ in Thousands
 6 Months Ended
Jun. 30, 2018
USD ($)
item
Real Estate Properties [Line Items]  
Number of Apartment Units | item 858
Total Development Costs $ 272,120
Unconsolidated Joint Venture Multi-Family Properties [Member]  
Real Estate Properties [Line Items]  
Number of Apartment Units | item 3,334
145 Front At City Square [Member] | Unconsolidated Joint Venture Multi-Family Properties [Member]  
Real Estate Properties [Line Items]  
Number of Apartment Units | item 365
Total Development Costs $ 98,669
Signature Place At Morris Plains [Member] | Unconsolidated Joint Venture Multi-Family Properties [Member]  
Real Estate Properties [Line Items]  
Number of Apartment Units | item 197
Total Development Costs $ 58,210
Portside 5/6 [Member] | Unconsolidated Joint Venture Multi-Family Properties [Member]  
Real Estate Properties [Line Items]  
Number of Apartment Units | item 296
Total Development Costs $ 115,241
Land [Member] | 145 Front At City Square [Member] | Unconsolidated Joint Venture Multi-Family Properties [Member]  
Real Estate Properties [Line Items]  
Total Development Costs 4,400
Land [Member] | Signature Place At Morris Plains [Member] | Unconsolidated Joint Venture Multi-Family Properties [Member]  
Real Estate Properties [Line Items]  
Total Development Costs 900
Construction Loan [Member] | 145 Front At City Square [Member]  
Real Estate Properties [Line Items]  
Expected costs 400
Construction Loan [Member] | Signature Place At Morris Plains [Member] | Unconsolidated Joint Venture Multi-Family Properties [Member]  
Real Estate Properties [Line Items]  
Expected costs 100
Construction Loan [Member] | Portside 5/6 [Member] | Unconsolidated Joint Venture Multi-Family Properties [Member]  
Real Estate Properties [Line Items]  
Expected costs $ 1,900