Annual report pursuant to Section 13 and 15(d)

Discontinued Operations (Narrative) (Details)

v3.20.4
Discontinued Operations (Narrative) (Details)
 1 Months Ended 12 Months Ended 15 Months Ended
Jan. 31, 2021
USD ($)
ft²
Dec. 31, 2020
USD ($)
ft²
property
item
Dec. 31, 2019
USD ($)
ft²
item
Dec. 31, 2020
USD ($)
ft²
item
property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]        
Unrealized losses on disposition of rental property   $ (14,040,000) $ (141,266,000)  
Book value   4,638,643,000 4,256,681,000 $ 4,638,643,000
Accumulated depreciation   $ 656,331,000 $ 558,617,000 $ 656,331,000
Area of property sold (in square feet) | ft²     4,490,578  
Suburban Office Portfolio [Member]        
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]        
Area of real estate property held for sale (in square feet) | ft²     6,600,000  
Suburban Office Portfolio [Member] | Holmdel, New Jersey [Member]        
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]        
Area of property (in square feet) | ft²   350,000   350,000
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]        
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]        
Properties | property   6    
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Disposal Group Three [Member]        
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]        
Number of disposal groups | item   3    
Unrealized losses on disposition of rental property   $ (14,000,000)    
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Properties Disposed One [Member] | Suburban Office Portfolio [Member]        
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]        
Area of real estate property held for sale (in square feet) | ft²   3,000,000.0   3,000,000.0
Number of disposal groups | property   6    
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Properties Disposed Two [Member] | Suburban Office Portfolio [Member]        
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]        
Number of real estate properties | property   16   16
Disposal Group, Not Discontinued Operations [Member]        
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]        
Number of properties sold | item   20 68  
Area of real estate property held for sale (in square feet) | ft²   2,725,639   2,725,639
Sales proceeds   $ 370,754,000 $ 1,052,427,000  
Gain (loss) on sale of property   7,163,000 $ 382,151,000  
Disposal Group, Not Discontinued Operations [Member] | Suburban Office Portfolio [Member] | Holmdel, New Jersey [Member]        
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]        
Book value   19,800,000   $ 19,800,000
Accumulated depreciation   10,500,000   10,500,000
Reversal of valuation allowance   $ 2,800,000   $ 2,800,000
Disposal Group, Not Discontinued Operations [Member] | Properties Disposed Two [Member] | Suburban Office Portfolio [Member]        
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]        
Number of real estate properties | property   15   15
Area of property (in square feet) | ft²   2,800,000   2,800,000
Gain (loss) on sale of property   $ 652,400,000    
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Suburban Office Properties [Member]        
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]        
Number of properties sold | item       20
Gain (loss) on sale of property   $ 377,400,000    
Area of property sold (in square feet) | ft²   3,200,000   3,200,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Properties Disposed Three [Member] | Suburban Office Portfolio [Member]        
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]        
Number of real estate properties | property   1   1
Subsequent Event [Member] | Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Properties Disposed Three [Member] | Suburban Office Portfolio [Member]        
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]        
Area of property (in square feet) | ft² 149,600      
Gain (loss) on sale of property $ 38,000,000