Quarterly report pursuant to Section 13 or 15(d)

Recent Transactions (Schedule Of Real Estate Held For Sale/Discontinued Operations/Dispositions) (Details)

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Recent Transactions (Schedule Of Real Estate Held For Sale/Discontinued Operations/Dispositions) (Details) - USD ($)
$ in Thousands
Mar. 31, 2021
Dec. 31, 2020
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]    
Less: Accumulated depreciation $ (668,452) $ (656,331)
Real estate held for sale, net 415,029 $ 656,963
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]    
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]    
Land 129,935  
Buildings & Other 522,942  
Less: Accumulated depreciation (120,780)  
Less: Cumulative unrealized losses on property held for sale (117,068)  
Real estate held for sale, net 415,029  
Unbilled rents receivable, net 13,356  
Deferred charges, net 9,326  
Total intangibles, net 17,464  
Total deferred charges & other assets, net 27,887  
Mortgages & loans payable, net 123,797  
Total below market liability 2,898  
Accounts payable, accrued exp & other liability 11,778  
Unearned rents/deferred rental income 6,050  
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Other Assets Held for Sale [Member]    
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]    
Land 76,396  
Buildings & Other 42,138  
Less: Accumulated depreciation (7,991)  
Less: Cumulative unrealized losses on property held for sale (40,731)  
Real estate held for sale, net 69,812  
Unbilled rents receivable, net 2,156  
Deferred charges, net 651  
Total deferred charges & other assets, net 683  
Accounts payable, accrued exp & other liability 136  
Unearned rents/deferred rental income 215  
Suburban Office Portfolio [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member]    
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]    
Land 53,539  
Buildings & Other 480,804  
Less: Accumulated depreciation (112,789)  
Less: Cumulative unrealized losses on property held for sale (76,337)  
Real estate held for sale, net 345,217  
Unbilled rents receivable, net 11,200  
Deferred charges, net 8,675  
Total intangibles, net 17,464  
Total deferred charges & other assets, net 27,204  
Mortgages & loans payable, net 123,797  
Total below market liability 2,898  
Accounts payable, accrued exp & other liability 11,642  
Unearned rents/deferred rental income $ 5,835