Quarterly report pursuant to Section 13 or 15(d)

Commitments And Contingencies (Construction Projects) (Narrative) (Details)

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Commitments And Contingencies (Construction Projects) (Narrative) (Details)
$ in Thousands
 6 Months Ended
Jun. 30, 2018
USD ($)
item
Dec. 31, 2017
USD ($)
Dec. 31, 2015
item
Commitments And Contingencies [Line Items]      
Number of units | item 858    
Amount outstanding $ 856,188 $ 822,288  
XS Hotel Urban Renewal Associates LLC [Member]      
Commitments And Contingencies [Line Items]      
Percentage of interest in venture     90.00%
Costs of the project incurred $ 126,400    
Delivery date to tenant fourth quarter 2018    
Number of units | item     372
Total project costs $ 142,500    
Port Imperial South 11 [Member]      
Commitments And Contingencies [Line Items]      
Costs of the project incurred $ 104,900    
Delivery date to tenant third quarter 2018    
Number of units | item 295    
Total project costs $ 122,000    
Construction Loan [Member] | XS Hotel Urban Renewal Associates LLC [Member]      
Commitments And Contingencies [Line Items]      
Maximum borrowing capacity 94,000    
Amount outstanding 65,600    
Construction Loan [Member] | Port Imperial South 11 [Member]      
Commitments And Contingencies [Line Items]      
Amount outstanding 60,100    
Amount to fund 78,000    
Development Property [Member] | Port Imperial South 11 [Member]      
Commitments And Contingencies [Line Items]      
Costs of the project incurred 41,600    
Amount to fund $ 44,000