Annual report pursuant to Section 13 and 15(d)

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

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Recent Transactions (Schedule Of Disposed Developable Land) (Details) - USD ($)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]    
Total Development Costs Incurred $ 105,477,000 $ 457,984,000
Land and other Impairments 32,444,000 24,566,000
Disposal Group, Not Discontinued Operations [Member]    
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]    
Net Sales Proceeds 18,383,000 46,036,000
Net Carrying Value 17,860,000 15,097,000
Gain on Disposition of Developable Land 523,000 30,939,000
1 Lake Street [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   46,036,000
Net Carrying Value   15,097,000
Gain on Disposition of Developable Land   30,939,000
Total Development Costs Incurred   3,000,000
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]    
Net Sales Proceeds 685,000  
Net Carrying Value 415,000  
Gain on Disposition of Developable Land 270,000  
Land and other Impairments   10,900,000
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]    
Net Sales Proceeds 1,135,000  
Net Carrying Value 839,000  
Gain on Disposition of Developable Land 296,000  
150 Monument Street [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 8,374,000  
Net Carrying Value 7,874,000  
Gain on Disposition of Developable Land 500,000  
51 Washington Street [Member]    
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]    
Land and other Impairments 2,700,000  
51 Washington Street [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 8,189,000  
Net Carrying Value 8,732,000  
Gain on Disposition of Developable Land $ (543,000)  
Land and other Impairments   $ 13,600,000