Quarterly report pursuant to Section 13 or 15(d)

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

v3.20.2
Recent Transactions (Real Estate Held For Sale/Discontinued Operations/Dispositions) (Narrative) (Details)
 1 Months Ended 3 Months Ended 9 Months Ended 21 Months Ended
Oct. 31, 2020
USD ($)
ft²
Sep. 30, 2020
USD ($)
ft²
property
item
Sep. 30, 2019
USD ($)
Sep. 30, 2020
USD ($)
ft²
item
property
Sep. 30, 2019
USD ($)
Sep. 30, 2020
USD ($)
ft²
property
item
Dec. 31, 2019
USD ($)
Dec. 19, 2019
ft²
Real Estate Properties [Line Items]                
Unrealized losses on rental properties held for sale       $ (7,915,000)        
Land and other impairments   $ 1,292,000 $ 2,589,000 23,401,000 $ 5,088,000      
Proceeds from the sale of property       16,455,000 $ 637,982,000      
Accumulated depreciation   627,995,000   627,995,000   $ 627,995,000 $ 558,617,000  
Book value   4,554,380,000   4,554,380,000   4,554,380,000 $ 4,256,681,000  
Suburban Office Portfolio [Member]                
Real Estate Properties [Line Items]                
Area of property (in square feet) | ft²               6,600,000
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]                
Real Estate Properties [Line Items]                
Accumulated depreciation   $ 227,848,000   $ 227,848,000   $ 227,848,000    
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Suburban Office Portfolio [Member]                
Real Estate Properties [Line Items]                
Number of real estate properties | item   12   12   12    
Accumulated depreciation   $ 219,857,000   $ 219,857,000   $ 219,857,000    
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Suburban Office Portfolio [Member]                
Real Estate Properties [Line Items]                
Number of disposal groups | item       12        
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   21   21   21    
Area of property (in square feet) | ft²   4,000,000   4,000,000   4,000,000    
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   21   21   21    
Area of property (in square feet) | ft²   4,000,000   4,000,000   4,000,000    
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Office [Member]                
Real Estate Properties [Line Items]                
Number of properties held for sale | property   21   21   21    
Number of disposal groups | property       12        
Disposal Group, Not Discontinued Operations [Member]                
Real Estate Properties [Line Items]                
Unrealized losses on rental properties held for sale       $ (33,314,000)        
Area Of Real Estate Property Sold | ft²   2,114,509   2,114,509   2,114,509    
Gain (loss) on sale of property       $ 9,414,000        
Disposal Group, Not Discontinued Operations [Member] | Suburban Office Portfolio [Member]                
Real Estate Properties [Line Items]                
Area of property (in square feet) | ft²   2,600,000   2,600,000   2,600,000    
Gain (loss) on sale of property           $ 294,800,000    
Disposal Group, Not Discontinued Operations [Member] | Suburban Office Portfolio [Member]                
Real Estate Properties [Line Items]                
Area of property (in square feet) | ft²   2,600,000   2,600,000   2,600,000    
Disposal Group, Not Discontinued Operations [Member] | Properties Disposed One [Member] | Suburban Office Portfolio [Member]                
Real Estate Properties [Line Items]                
Number of properties sold | property           16    
Disposal Group, Not Discontinued Operations [Member] | Properties Disposed Two [Member] | Suburban Office Portfolio [Member]                
Real Estate Properties [Line Items]                
Number of real estate properties | property   10   10   10    
Area of property (in square feet) | ft²   1,900,000   1,900,000   1,900,000    
Gain (loss) on sale of property       $ 407,500,000        
Disposal Group, Not Discontinued Operations [Member] | Properties Disposed Two [Member] | Suburban Office Portfolio [Member]                
Real Estate Properties [Line Items]                
Number of real estate properties | property   10   10   10    
Area of property (in square feet) | ft²   1,900,000   1,900,000   1,900,000    
Gain (loss) on sale of property       $ 407,500,000        
Disposal Group, Not Discontinued Operations [Member] | Properties Disposed Three [Member] | Subsequent Event [Member] | Suburban Office Portfolio [Member]                
Real Estate Properties [Line Items]                
Area of property (in square feet) | ft² 98,500              
Gain (loss) on sale of property $ 7,500,000              
Parsippany, Madison, Short Hills, Edison, And Red Bank, New Jersey [Member]                
Real Estate Properties [Line Items]                
Unrealized losses on rental properties held for sale   $ 0   41,200,000        
Land and other impairments   $ 1,300,000   $ 23,400,000        
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   10   10   10    
Number of disposal groups | item       5        
Parsippany, Madison, Short Hills, Edison, And Red Bank, New Jersey [Member] | Discontinued Operations [Member]                
Real Estate Properties [Line Items]                
Unrealized losses on rental properties held for sale   $ 0   $ 33,300,000        
Land and other impairments   $ 1,300,000   $ 23,400,000        
Hoboken, New Jersey [Member]                
Real Estate Properties [Line Items]                
Area of property (in square feet) | ft²   566,215   566,215   566,215    
Accumulated depreciation   $ 25,400,000   $ 25,400,000   $ 25,400,000    
Book value   $ 194,400,000   194,400,000   $ 194,400,000    
Catch-up depreciation and amortization expense       $ 3,800,000        
Development [Member] | 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 | item   2   2   2