Quarterly report pursuant to Section 13 or 15(d)

Mack-Cali Realty Corporation Stockholders' Equity And Mack-Cali Realty, L.P.'s Partners' Capital (AO LTIP Units (Appreciation-Only LTIP Units)) (Narrative) (Details)

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Mack-Cali Realty Corporation Stockholders' Equity And Mack-Cali Realty, L.P.'s Partners' Capital (AO LTIP Units (Appreciation-Only LTIP Units)) (Narrative) (Details) - USD ($)
3 Months Ended 9 Months Ended 15 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Mar. 31, 2019
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock options expense $ 253,000 $ 192,000   $ 591,000 $ 192,000  
AO LTIP Units Award [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Share price $ 21.46     $ 21.46   $ 21.46
Exercisable period       10 years    
Total unrecognized compensation cost $ 900,000     $ 900,000   $ 900,000
Total unrecognized compensation cost, period of recognition       1 year 4 months 24 days    
Stock options expense       $ 466,000 $ 466,000 $ 156,000
AO LTIP Units Award [Member] | Messr DeMarco, CEO [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares granted     625,000      
Income allocation       10.00%    
Percent of cash distribution       10.00%    
AO LTIP Units Award [Member] | Messr DeMarco, CEO [Member] | Tranche One [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares to be vested and exercisable       250,000    
Common stock trading days       30 days    
Common stock trade share price       $ 25.00    
Common stock expiration date       Mar. 13, 2023    
AO LTIP Units Award [Member] | Messr DeMarco, CEO [Member] | Tranche Two [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares to be vested and exercisable       250,000    
Common stock trading days       30 days    
Common stock trade share price       $ 28.00    
AO LTIP Units Award [Member] | Messr DeMarco, CEO [Member] | Tranche Three [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares to be vested and exercisable       125,000    
Common stock trading days       30 days    
Common stock trade share price       $ 31.00