Quarterly report pursuant to Section 13 or 15(d)

Organization And Basis Of Presentation (Narrative) (Details)

v3.20.2
Organization And Basis Of Presentation (Narrative) (Details)
$ in Millions
 9 Months Ended
Sep. 30, 2020
USD ($)
ft²
property
state
item
room
Dec. 31, 2019
USD ($)
Dec. 19, 2019
ft²
Real Estate Properties [Line Items]      
Percentage of ownership interest 90.40% 90.40%  
Number of properties owned or investment interests 59    
Number of states where properties are located | state 4    
Consolidated joint ventures, total real estate assets | $ $ 493.1 $ 503.1  
Consolidated joint ventures, mortgages | $ 284.2 283.7  
Consolidated joint ventures, other liabilities | $ 21.0 $ 18.9  
Increase in land and other impairments | $ $ 2.5    
Commercial Properties [Member]      
Real Estate Properties [Line Items]      
Number of tenants | item 225    
Multi-Family Properties [Member]      
Real Estate Properties [Line Items]      
Number of properties owned or investment interests 22    
Number of units | item 6,850    
Office [Member]      
Real Estate Properties [Line Items]      
Number of properties owned or investment interests 29    
Aggregate square feet of the property owned or investment interest | ft² 8,700,000    
Unconsolidated Joint Venture Office Buildings [Member]      
Real Estate Properties [Line Items]      
Number of properties owned or investment interests 2    
Aggregate square feet of the property owned or investment interest | ft² 200,000    
Area of property (in square feet) | ft² 200,000    
Unconsolidated Joint Venture Multi-Family Properties [Member]      
Real Estate Properties [Line Items]      
Number of properties owned or investment interests 7    
Number of units | item 2,611    
Unconsolidated Joint Venture Office/Flex Buildings And Hotel [Member]      
Real Estate Properties [Line Items]      
Number of properties owned or investment interests 3    
Number of units | room 723    
Parking/Retail [Member]      
Real Estate Properties [Line Items]      
Number of properties owned or investment interests 4    
Aggregate square feet of the property owned or investment interest | ft² 108,000    
Unconsolidated Joint Venture Parking/Retail Buildings [Member]      
Real Estate Properties [Line Items]      
Number of properties owned or investment interests 1    
Aggregate square feet of the property owned or investment interest | ft² 51,000    
Land [Member]      
Real Estate Properties [Line Items]      
Number of properties owned or investment interests 1    
Suburban Office Portfolio [Member]      
Real Estate Properties [Line Items]      
Area of property (in square feet) | ft²     6,600,000