Quarterly report pursuant to Section 13 or 15(d)

Discontinued Operations (Narrative) (Details)

v3.21.1
Discontinued Operations (Narrative) (Details)
$ in Thousands, ft² in Millions
1 Months Ended 3 Months Ended 27 Months Ended
Apr. 30, 2021
USD ($)
property
Mar. 31, 2021
USD ($)
ft²
property
item
Mar. 31, 2020
USD ($)
Mar. 31, 2021
USD ($)
ft²
property
Dec. 19, 2019
ft²
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]          
Unrealized gains (losses) on disposition of rental property   $ 1,020 $ (45,068)    
Proceeds from the sale of property     $ 6,939    
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         6.6
Disposal Group One [Member]          
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]          
Properties | property   1      
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Short Hills, New Jersey [Member]          
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]          
Gain (loss) on sale of property   $ 2,200      
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Suburban Office Portfolio [Member]          
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]          
Number of disposal groups | item   4      
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Disposal Group One [Member]          
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]          
Unrealized gains (losses) on disposition of rental property   $ (1,200)      
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]          
Number of real estate properties | property   11   11  
Area of property (in square feet) | ft²   2.0   2.0  
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   5      
Sales proceeds   $ 282,075      
Gain (loss) on sale of property   $ 21,761      
Disposal Group, Not Discontinued Operations [Member] | Suburban Office Portfolio [Member]          
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]          
Number of properties sold | property       25  
Sales proceeds       $ 659,400  
Area of property (in square feet) | ft²   4.3   4.3  
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]          
Gain (loss) on sale of property   $ 391,400      
Subsequent Event [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Short Hills, New Jersey [Member]          
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]          
Number of properties sold | property 4        
Number of properties sold | property 4        
Gain (loss) on sale of property $ 2,200        
Proceeds from the sale of property 255,000        
Net proceeds $ 100,000