Commitments And Contingencies (Construction Projects) (Narrative) (Details)
 12 Months Ended
Dec. 31, 2016
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Dec. 31, 2015
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Dec. 31, 2014
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Sep. 30, 2016
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Commitments And Contingencies [Line Items]        
Amount outstanding $ 634,069,000 $ 155,000,000    
Investment in unconsolidated joint ventures 35,930,000 $ 78,027,000 $ 67,325,000  
XS Hotel Urban Renewal Associates LLC [Member]        
Commitments And Contingencies [Line Items]        
Percentage of interest in venture   90.00%    
Costs of the project incurred 55,800,000      
Number of units | item   372    
Total project costs 129,600,000      
City Square Project [Member]        
Commitments And Contingencies [Line Items]        
Costs of the project incurred 34,500,000      
Total project costs $ 92,000,000      
City Square Project Phase One [Member]        
Commitments And Contingencies [Line Items]        
Delivery date to tenant fourth quarter 2017      
Number of units | item   237    
City Square Project Phase Two [Member]        
Commitments And Contingencies [Line Items]        
Delivery date to tenant third quarter 2018      
Number of units | item       128
Signature Place Project [Member]        
Commitments And Contingencies [Line Items]        
Costs of the project incurred $ 18,600,000      
Delivery date to tenant fourth quarter of 2017      
Number of units | item 197      
Total project costs $ 58,700,000      
Portside 5/6 Project [Member]        
Commitments And Contingencies [Line Items]        
Delivery date to tenant second quarter 2018      
Number of units | item 296      
Total project costs $ 111,400,000      
Riverhouse 11 Project [Member]        
Commitments And Contingencies [Line Items]        
Costs of the project incurred $ 42,000,000      
Delivery date to tenant first quarter 2018      
Number of units | item 295      
Total project costs $ 124,000,000      
51 Washington Street Project [Member]        
Commitments And Contingencies [Line Items]        
Costs of the project incurred $ 21,700,000      
Delivery date to tenant fourth quarter 2018      
Number of units | item 310      
Total project costs $ 89,400,000      
Amount to fund 35,400,000      
Construction Loan [Member] | XS Hotel Urban Renewal Associates LLC [Member]        
Commitments And Contingencies [Line Items]        
Maximum borrowing capacity 94,000,000      
Amount outstanding 14,900,000      
Construction Loan [Member] | City Square Project [Member]        
Commitments And Contingencies [Line Items]        
Maximum borrowing capacity 58,000,000      
Amount outstanding 0      
Construction Loan [Member] | Signature Place Project [Member]        
Commitments And Contingencies [Line Items]        
Amount to fund 42,000,000      
Construction Loan [Member] | Portside 5/6 Project [Member]        
Commitments And Contingencies [Line Items]        
Amount to fund 73,000,000      
Construction Loan [Member] | Riverhouse 11 Project [Member]        
Commitments And Contingencies [Line Items]        
Amount to fund 78,000,000      
Construction Loan [Member] | 51 Washington Street Project [Member]        
Commitments And Contingencies [Line Items]        
Amount to fund 54,000,000      
Development Property [Member] | Portside 5/6 Project [Member]        
Commitments And Contingencies [Line Items]        
Costs of the project incurred 35,300,000      
Amount to fund 38,400,000      
Development Property [Member] | Riverhouse 11 Project [Member]        
Commitments And Contingencies [Line Items]        
Costs of the project incurred 27,900,000      
Amount to fund $ 46,000,000      
Unconsolidated Joint Venture Hotel [Member]        
Commitments And Contingencies [Line Items]        
Number of units | item 350      
Unconsolidated Joint Venture Hotel [Member] | Harborside Unit A Urban Renewal, LLC [Member]        
Commitments And Contingencies [Line Items]        
Percentage of interest in venture     85.00%  
Costs of the project incurred $ 301,100,000      
Delivery date to tenant first quarter 2017      
Number of units | item     763  
Amount outstanding $ 155,200,000      
Total project costs 320,000,000      
Unconsolidated Joint Venture Hotel [Member] | Construction/Permanent Loan [Member] | Harborside Unit A Urban Renewal, LLC [Member]        
Commitments And Contingencies [Line Items]        
Maximum borrowing capacity $ 192,000,000