Recent Transactions (Schedule Of Properties Which Commenced Initial Operations) (Details)
$ in Thousands
 12 Months Ended
Dec. 31, 2016
USD ($)
item
Dec. 31, 2017
item
Unconsolidated Joint Venture Multi-Family Properties [Member]    
Real Estate Properties [Line Items]    
Number of Apartment Units | item   3,275
Quarry Place At Tuckahoe [Member] | Unconsolidated Joint Venture Multi-Family Properties [Member]    
Real Estate Properties [Line Items]    
Number of Apartment Units | item 108  
Development Costs Incurred by Company [1] $ 56,961  
The Chase II At Overlook Ridge [Member] | Unconsolidated Joint Venture Multi-Family Properties [Member]    
Real Estate Properties [Line Items]    
Number of Apartment Units | item 292  
Development Costs Incurred by Company [2] $ 65,218  
Quarry Place At Tuckahoe And The Chase II At Overlook Ridge [Member] | Unconsolidated Joint Venture Multi-Family Properties [Member]    
Real Estate Properties [Line Items]    
Number of Apartment Units | item 400  
Development Costs Incurred by Company $ 122,179  
Land [Member] | Quarry Place At Tuckahoe [Member]    
Real Estate Properties [Line Items]    
Development Costs Incurred by Company 5,600  
Land [Member] | The Chase II At Overlook Ridge [Member]    
Real Estate Properties [Line Items]    
Development Costs Incurred by Company 10,800  
Construction Loan [Member] | The Chase II At Overlook Ridge [Member]    
Real Estate Properties [Line Items]    
Expected costs $ 9,700  
[1] Development costs as of December 31, 2016 included approximately $5.6 million in land costs.
[2] Development costs as of December 31, 2016 included approximately $10.8 million in land costs. As of December 31, 2016, the Company anticipates additional costs of approximately $9.7 million, which will be funded from a construction loan.