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 6 Months Ended
Jun. 30, 2020
USD ($)
item
property
Jun. 30, 2019
USD ($)
Jun. 30, 2020
USD ($)
property
item
Jun. 30, 2019
USD ($)
Dec. 31, 2019
USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Fair value of Company's long-term debt $ 3,032,589,000   $ 3,032,589,000   $ 2,791,629,000
Principal balance outstanding 2,990,465,000   2,990,465,000   $ 2,808,517,000
Unrealized losses on rental properties held for sale     (7,915,000)    
Properties aggregate net book value     1,100,000    
Land and other Impairments 16,846,000 $ 2,499,000 22,109,000 $ 2,499,000  
Parsippany, Madison, Short Hills, Edison, Red Bank, and Florham Park [Member]          
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Unrealized losses on rental properties held for sale $ 11,900,000   64,900,000    
Land and other Impairments   $ 16,800,000 $ 22,100,000    
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Parsippany, Madison, Short Hills, Edison, Red Bank, and Florham Park [Member]          
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Number of properties held for sale | property 21   21    
Number of disposal groups | item     7    
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 35   35    
Number of disposal groups | property     13    
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     $ (56,997,000)    
Discontinued Operations [Member] | Parsippany, Madison, Short Hills, Edison, Red Bank, and Florham Park [Member]          
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Unrealized losses on rental properties held for sale $ 11,900,000   57,000,000.0    
Land and other Impairments $ 16,800,000   $ 22,100,000    
Development [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Parsippany, Madison, Short Hills, Edison, Red Bank, and Florham Park [Member]          
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Number of properties held for sale | item 2   2