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)
$ in Thousands
3 Months Ended 6 Months Ended 18 Months Ended
Jun. 30, 2020
USD ($)
ft²
property
item
Jun. 30, 2019
USD ($)
Jun. 30, 2020
USD ($)
ft²
property
item
Jun. 30, 2019
USD ($)
Jun. 30, 2020
USD ($)
ft²
property
item
Dec. 19, 2019
ft²
Real Estate Properties [Line Items]            
Unrealized losses on rental properties held for sale     $ (7,915)      
Land and other Impairments $ 16,846 $ 2,499 22,109 $ 2,499    
Proceeds from the sale of property     $ 16,455 $ 636,161    
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 13   13   13  
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 34   34   34  
Area of property (in square feet) | ft² 5,900,000   5,900,000   5,900,000  
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Office [Member]            
Real Estate Properties [Line Items]            
Number of properties held for sale | property 35   35   35  
Number of disposal groups | property     13      
Disposal Group, Not Discontinued Operations [Member]            
Real Estate Properties [Line Items]            
Unrealized losses on rental properties held for sale     $ (56,997)      
Area Of Real Estate Property Sold | ft² 200,000   200,000   200,000  
Gain (loss) on sale of property     $ 17,322      
Disposal Group, Not Discontinued Operations [Member] | Suburban Office Portfolio [Member]            
Real Estate Properties [Line Items]            
Area of property (in square feet) | ft² 697,000   697,000   697,000  
Gain (loss) on sale of property         $ 87,200  
Disposal Group, Not Discontinued Operations [Member] | 111 River St. [Member]            
Real Estate Properties [Line Items]            
Area of property (in square feet) | ft² 566,215   566,215   566,215  
Gain (loss) on sale of property     $ 244,500      
Disposal Group, Not Discontinued Operations [Member] | Properties Disposed One [Member] | Suburban Office Portfolio [Member]            
Real Estate Properties [Line Items]            
Number of properties sold | property         3  
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 17   17   17  
Area of property (in square feet) | ft² 2,700,000   2,700,000   2,700,000  
Gain (loss) on sale of property     $ 305,400      
Parsippany, Madison, Short Hills, Edison, Red Bank, and Florham Park [Member]            
Real Estate Properties [Line Items]            
Unrealized losses on rental properties held for sale $ 11,900   64,900      
Land and other Impairments   $ 16,800 $ 22,100      
Parsippany, Madison, Short Hills, Edison, Red Bank, and Florham Park [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member]            
Real Estate Properties [Line Items]            
Number of properties held for sale | property 21   21   21  
Number of disposal groups | item     7      
Parsippany, Madison, Short Hills, Edison, Red Bank, and Florham Park [Member] | Discontinued Operations [Member]            
Real Estate Properties [Line Items]            
Unrealized losses on rental properties held for sale $ 11,900   $ 57,000      
Land and other Impairments $ 16,800   $ 22,100      
Development [Member] | Parsippany, Madison, Short Hills, Edison, Red Bank, and Florham Park [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