Annual report pursuant to Section 13 and 15(d)

Recent Transactions (Consolidations) (Narrative) (Details)

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Recent Transactions (Consolidations) (Narrative) (Details)
1 Months Ended 12 Months Ended
Aug. 02, 2018
USD ($)
item
Feb. 28, 2017
USD ($)
ft²
item
shares
Feb. 03, 2017
USD ($)
shares
Apr. 30, 2017
USD ($)
shares
Dec. 31, 2018
USD ($)
item
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Aug. 01, 2018
USD ($)
Feb. 27, 2017
Feb. 02, 2017
Real Estate Properties [Line Items]                    
Acquisition cost         $ 11,789,000 $ 36,060,000 $ 35,930,000      
Consolidated joint ventures, total real estate assets         $ 480,400,000 215,500,000        
Net assets acquired           $ 394,589,000        
Percentage of ownership interest         89.80% 89.60%        
Number of units | item         1,317          
Purchase price of property         $ 168,398,000 $ 90,068,000 121,582,000      
Gain on sale of investment in unconsolidated joint venture           23,131,000 5,670,000      
Mortgage loan         45,242,000 45,734,000      
Gain on change of control of interests         14,217,000   15,347,000      
Issuance of loan         30,400,000          
Loan balance         2,792,651,000 2,809,568,000        
Noncontrolling interest's fair value         210,523,000 192,428,000        
Mack-Cali Realty LP [Member]                    
Real Estate Properties [Line Items]                    
Acquisition cost         11,789,000 36,060,000 35,930,000      
Purchase price of property         168,398,000 90,068,000 121,582,000      
Gain on sale of investment in unconsolidated joint venture           $ 23,131,000 5,670,000      
Gain on change of control of interests         14,217,000   $ 15,347,000      
Plaza VIII & IX Associates, L.L.C. [Member]                    
Real Estate Properties [Line Items]                    
Percentage of interest in venture                   50.00%
Percentage of additional interest acquired     12.50%              
Acquisition cost     $ 14,300,000              
Consolidated joint ventures, total real estate assets     $ 60,600,000              
Monaco [Member]                    
Real Estate Properties [Line Items]                    
Number of towers | item   2                
Net assets acquired         $ 139,886,000          
Garage Parking Spaces | item   558                
Number of stories | item   50                
Area of property (in square feet) | ft²   12,300                
Number of units | item   523                
Marbella Tower Urban Renewal Associates LLC [Member]                    
Real Estate Properties [Line Items]                    
Percentage of interest in venture               24.27%    
Percentage of additional interest acquired 50.00%                  
Number of units | item 412                  
Purchase price of property $ 65,600,000                  
Mortgage loan, maturity date         Aug. 01, 2026          
Spread over LIBOR 4.07%                  
Mortgage loan $ 131,000,000             $ 95,000,000    
Gain on change of control of interests         $ 14,200,000          
Repayment of mortgage loans $ 95,000,000                  
Issuance of loan         37,400,000          
Loan balance         14,000,000          
Noncontrolling interest's fair value         $ 29,800,000          
Series A Units [Member] | Mack-Cali Realty LP [Member]                    
Real Estate Properties [Line Items]                    
Preferred units shares issued | shares     42,800              
Percentage of interest in venture     37.50%              
Preferred unit annual rate     3.50%              
Preferred units aggregate amount     $ 42,800,000              
Series A-1 Units [Member]                    
Real Estate Properties [Line Items]                    
Percentage of ownership interest   29.00%                
Series A-1 Units [Member] | Mack-Cali Realty LP [Member]                    
Real Estate Properties [Line Items]                    
Preferred units shares issued | shares   9,213   91            
Percentage of interest in venture   13.80%                
Preferred unit annual rate   3.50%                
Series A-1 Units [Member] | Monaco [Member]                    
Real Estate Properties [Line Items]                    
Percentage of interest in venture   29.00%             13.80%  
Series A-1 Units [Member] | Monaco [Member] | Mack-Cali Realty LP [Member]                    
Real Estate Properties [Line Items]                    
Preferred units shares issued | shares   9,122   91            
Percentage of interest in venture       71.20%            
Preferred units aggregate amount   $ 9,100,000                
Acquisition cost       $ 130,900,000            
Debt assumed       $ 171,200,000