Commitments And Contingencies (Construction Projects) (Narrative) (Details)
$ in Thousands
 3 Months Ended
Mar. 31, 2017
USD ($)
item
Mar. 31, 2016
USD ($)
Dec. 31, 2016
USD ($)
item
Dec. 31, 2015
item
Dec. 31, 2014
item
Commitments And Contingencies [Line Items]          
Amount outstanding $ 760,937   $ 634,069    
Investment in unconsolidated joint ventures 6,625 $ 7,225      
Amount to fund 35,400        
XS Hotel Urban Renewal Associates LLC [Member]          
Commitments And Contingencies [Line Items]          
Percentage of interest in venture       90.00%  
Costs of the project incurred 64,700        
Number of units | item       372  
Total project costs 129,600        
City Square Project [Member]          
Commitments And Contingencies [Line Items]          
Costs of the project incurred 44,700        
Total project costs $ 92,000        
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 $ 26,900        
Delivery date to tenant fourth quarter of 2017        
Number of units | item     197    
Total project costs $ 58,700        
Portside 5/6 Project [Member]          
Commitments And Contingencies [Line Items]          
Costs of the project incurred $ 48,100        
Delivery date to tenant second quarter 2018        
Number of units | item 296        
Total project costs $ 111,400        
Riverhouse 11 Project [Member]          
Commitments And Contingencies [Line Items]          
Costs of the project incurred $ 52,500        
Delivery date to tenant first quarter 2018        
Number of units | item 295        
Total project costs $ 124,000        
51 Washington Street Project [Member]          
Commitments And Contingencies [Line Items]          
Costs of the project incurred $ 22,400        
Delivery date to tenant second quarter 2019        
Number of units | item 310        
Total project costs $ 89,400        
Construction Loan [Member] | XS Hotel Urban Renewal Associates LLC [Member]          
Commitments And Contingencies [Line Items]          
Maximum borrowing capacity 94,000        
Amount outstanding 24,500        
Construction Loan [Member] | City Square Project [Member]          
Commitments And Contingencies [Line Items]          
Maximum borrowing capacity 58,000        
Amount outstanding 5,000        
Construction Loan [Member] | Signature Place Project [Member]          
Commitments And Contingencies [Line Items]          
Amount outstanding 6,100        
Amount to fund 42,000        
Construction Loan [Member] | Portside 5/6 Project [Member]          
Commitments And Contingencies [Line Items]          
Amount outstanding 8,100        
Amount to fund 73,000        
Construction Loan [Member] | Riverhouse 11 Project [Member]          
Commitments And Contingencies [Line Items]          
Amount outstanding 22,200        
Amount to fund 78,000        
Construction Loan [Member] | 51 Washington Street Project [Member]          
Commitments And Contingencies [Line Items]          
Amount to fund 54,000        
Development Property [Member] | Riverhouse 11 Project [Member]          
Commitments And Contingencies [Line Items]          
Costs of the project incurred 30,300        
Amount to fund $ 46,000        
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 $ 308,600        
Delivery date to tenant second quarter 2017        
Number of units | item         762
Amount outstanding $ 173,900        
Total project costs 320,000        
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