Annual report pursuant to Section 13 and 15(d)

Recent Transactions (Schedule Of Disposed Developable Land) (Details)

v3.20.4
Recent Transactions (Schedule Of Disposed Developable Land) (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Net Sales Proceeds   $ 18,383  
Net Carrying Value   17,860  
Realized Gains (losses)/Unrealized Losses, net   523  
Land impairments $ 16,817 32,444 $ 24,566
Disposal Group, Not Discontinued Operations [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Net Sales Proceeds 18,917    
Net Carrying Value 13,130    
Realized Gains (losses)/Unrealized Losses, net 5,787    
230 & 250 Half Mile Road [Member] | Disposal Group, Not Discontinued Operations [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Net Sales Proceeds 7,018    
Net Carrying Value 2,969    
Realized Gains (losses)/Unrealized Losses, net 4,049    
Capital Office Park Land [Member] | Disposal Group, Not Discontinued Operations [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Net Sales Proceeds 8,974    
Net Carrying Value 8,210    
Realized Gains (losses)/Unrealized Losses, net 764    
Fourteen And Sixteen Skyline Drive [Member] | Disposal Group, Not Discontinued Operations [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Net Sales Proceeds 2,925    
Net Carrying Value 1,951    
Realized Gains (losses)/Unrealized Losses, net $ 974    
The Chase At Overlook Ridge [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Net Sales Proceeds   685  
Net Carrying Value   415  
Realized Gains (losses)/Unrealized Losses, net   270  
The Chase At Overlook Ridge [Member] | Disposal Group, Not Discontinued Operations [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Land impairments     10,900
Alterra At Overlook Ridge IA [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Net Sales Proceeds   1,135  
Net Carrying Value   839  
Realized Gains (losses)/Unrealized Losses, net   296  
Alterra At Overlook Ridge IA [Member] | Disposal Group, Not Discontinued Operations [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Land impairments   2,700 $ 13,600
150 Monument Street [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Net Sales Proceeds   8,374  
Net Carrying Value   7,874  
Realized Gains (losses)/Unrealized Losses, net   500  
51 Washington Street [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Net Sales Proceeds   8,189  
Net Carrying Value   8,732  
Realized Gains (losses)/Unrealized Losses, net   $ (543)