Quarterly report pursuant to Section 13 or 15(d)

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

v3.21.1
Recent Transactions (Real Estate Held For Sale/Discontinued Operations/Dispositions) (Narrative) (Details)
$ in Thousands
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
item
Dec. 31, 2020
USD ($)
Dec. 19, 2019
ft²
Real Estate Properties [Line Items]            
Land and other impairments   $ 413 $ 5,263      
Proceeds from the sale of property     $ 6,939      
Book value   $ 4,693,858   $ 4,693,858 $ 4,638,643  
Suburban Office Portfolio [Member]            
Real Estate Properties [Line Items]            
Area of property (in square feet) | ft²           6,600,000
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Suburban Office Portfolio [Member]            
Real Estate Properties [Line Items]            
Number of real estate properties | item   4   4    
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Subsequent Event [Member]            
Real Estate Properties [Line Items]            
Repayment of debt $ 124,500          
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Properties Disposed One [Member] | Suburban Office Portfolio [Member]            
Real Estate Properties [Line Items]            
Number of real estate properties | property   11   11    
Area of property (in square feet) | ft²   2,000,000   2,000,000    
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Office [Member]            
Real Estate Properties [Line Items]            
Number of properties held for sale | property   11   11    
Number of disposal groups | property   4        
Disposal Group, Not Discontinued Operations [Member]            
Real Estate Properties [Line Items]            
Unrealized gains (losses) on real estate held for sale   $ 1,020        
Area Of Real Estate Property Sold | ft²   1,076,256   1,076,256    
Gain (loss) on sale of property   $ 21,761        
Disposal Group, Not Discontinued Operations [Member] | Suburban Office Portfolio [Member]            
Real Estate Properties [Line Items]            
Area of property (in square feet) | ft²   4,300,000   4,300,000    
Gain (loss) on sale of property       $ 659,400    
Disposal Group, Not Discontinued Operations [Member] | Properties Disposed One [Member] | Suburban Office Portfolio [Member]            
Real Estate Properties [Line Items]            
Number of properties sold | property       25    
Disposal Group, Not Discontinued Operations [Member] | Properties Disposed Two [Member] | Suburban Office Portfolio [Member]            
Real Estate Properties [Line Items]            
Gain (loss) on sale of property   $ 391,400        
Parsippany, Madison, Short Hills, Edison, And Red Bank, New Jersey [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member]            
Real Estate Properties [Line Items]            
Number of properties held for sale | property   1   1    
Unrealized gains (losses) on real estate held for sale   $ 1,200        
Land and other impairments   400        
Parsippany, Madison, Short Hills, Edison, And Red Bank, New Jersey [Member] | Discontinued Operations [Member]            
Real Estate Properties [Line Items]            
Unrealized gains (losses) on real estate held for sale   1,200        
Land and other impairments   400        
Short Hills, New Jersey [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member]            
Real Estate Properties [Line Items]            
Gain (loss) on sale of property   $ 2,200        
Short Hills, New Jersey [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Subsequent Event [Member]            
Real Estate Properties [Line Items]            
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          
Repayment of debt $ 22,000