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 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Mar. 31, 2019
Jun. 30, 2021
Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Stock options expense $ 224,000 $ 0   $ 338,000 $ 0
AO LTIP Units Award [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share price $ 21.46     $ 21.46  
Exercisable period       10 years  
Total unrecognized compensation cost $ 1,100,000     $ 1,100,000  
Total unrecognized compensation cost, period of recognition       1 year 8 months 12 days  
Stock options expense $ 155,000 $ 155,000   $ 310,000 $ 310,000
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