Quarterly report pursuant to Section 13 or 15(d)

Disclosure Of Fair Value Of Assets And Liabilities (Narrative) (Details)

v3.20.2
Disclosure Of Fair Value Of Assets And Liabilities (Narrative) (Details)
 3 Months Ended 9 Months Ended
Sep. 30, 2020
USD ($)
property
item
Sep. 30, 2019
USD ($)
Sep. 30, 2020
USD ($)
item
property
Sep. 30, 2019
USD ($)
Dec. 31, 2019
USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Fair value of Company's long-term debt $ 2,963,488,000   $ 2,963,488,000   $ 2,791,629,000
Principal balance outstanding 2,895,882,000   2,895,882,000   $ 2,808,517,000
Unrealized losses on rental properties held for sale     (7,915,000)    
Properties aggregate net book value     714,400,000    
Land and other impairments 1,292,000 $ 2,589,000 23,401,000 $ 5,088,000  
Property impairments 36,582,000   36,582,000    
Parsippany, Madison, Short Hills, Edison, And Red Bank, New Jersey [Member]          
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Unrealized losses on rental properties held for sale 0   41,200,000    
Land and other impairments $ 1,300,000   $ 23,400,000    
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Parsippany, Madison, Short Hills, Edison, And Red Bank, New Jersey [Member]          
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Number of properties held for sale | property 10   10    
Number of disposal groups | item     5    
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Office [Member]          
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Number of properties held for sale | property 21   21    
Number of disposal groups | property     12    
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Retail Property [Member]          
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Number of properties held for sale | property 1   1    
Disposal Group, Not Discontinued Operations [Member]          
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Unrealized losses on rental properties held for sale     $ (33,314,000)    
Discontinued Operations [Member] | Parsippany, Madison, Short Hills, Edison, And Red Bank, New Jersey [Member]          
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Unrealized losses on rental properties held for sale $ 0   33,300,000    
Land and other impairments $ 1,300,000   $ 23,400,000    
Development [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Parsippany, Madison, Short Hills, Edison, And Red Bank, New Jersey [Member]          
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Number of properties held for sale | item 2   2