Quarterly report pursuant to Section 13 or 15(d)

Recent Transactions (Schedule Of Disposed Properties) (Details)

v3.20.2
Recent Transactions (Schedule Of Disposed Properties) (Details)
$ in Thousands
 9 Months Ended
Sep. 30, 2020
USD ($)
ft²
item
Dec. 31, 2019
USD ($)
Dec. 31, 2017
USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Unrealized losses on rental properties held for sale $ (7,915)    
Totals (7,915)    
Valuation allowance $ 18,500   $ 5,300
Disposal Group, Not Discontinued Operations [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Number of Buildings, Disposed | item 14    
Rentable Square Feet, Disposed | ft² 2,114,509    
Net Sales Proceeds $ 242,645    
Net Carrying Value 233,231    
Realized Gains (losses)/Unrealized Losses, net 9,414    
Unrealized losses on rental properties held for sale (33,314)    
Totals $ (23,900)    
Disposal Group, Not Discontinued Operations [Member] | One Bridge Plaza [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Number of Buildings, Disposed | item 1    
Rentable Square Feet, Disposed | ft² 200,000    
Net Sales Proceeds $ 35,065    
Net Carrying Value 17,743    
Realized Gains (losses)/Unrealized Losses, net $ 17,322    
Disposal Group, Not Discontinued Operations [Member] | 3 Giralda Farms [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Number of Buildings, Disposed | item 1    
Rentable Square Feet, Disposed | ft² 141,000    
Net Sales Proceeds $ 7,510    
Net Carrying Value 9,534    
Realized Gains (losses)/Unrealized Losses, net (2,024)    
Valuation allowance $ 2,000 $ 16,700  
Disposal Group, Not Discontinued Operations [Member] | Morris Portfolio [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Number of Buildings, Disposed | item 10    
Rentable Square Feet, Disposed | ft² 1,448,420    
Net Sales Proceeds $ 155,116    
Net Carrying Value 175,772    
Realized Gains (losses)/Unrealized Losses, net (20,656)    
Valuation allowance $ 21,600 32,500  
Disposal Group, Not Discontinued Operations [Member] | 325 Columbia Turnpike [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Number of Buildings, Disposed | item 1    
Rentable Square Feet, Disposed | ft² 168,144    
Net Sales Proceeds $ 24,276    
Net Carrying Value 8,020    
Realized Gains (losses)/Unrealized Losses, net $ 16,256    
Disposal Group, Not Discontinued Operations [Member] | 9 Campus Drive [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Number of Buildings, Disposed | item 1    
Rentable Square Feet, Disposed | ft² 156,945    
Net Sales Proceeds $ 20,678    
Net Carrying Value 22,162    
Realized Gains (losses)/Unrealized Losses, net $ (1,484)    
Valuation allowance   $ 3,500