Quarterly report pursuant to Section 13 or 15(d)

Mack-Cali Realty Corporation Stockholders' Equity And Mack-Cali Realty, L.P.'s Partners' Capital (Stock Option Plans) (Narrative) (Details)

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Mack-Cali Realty Corporation Stockholders' Equity And Mack-Cali Realty, L.P.'s Partners' Capital (Stock Option Plans) (Narrative) (Details)
3 Months Ended 12 Months Ended
Mar. 10, 2021
$ / shares
shares
Jul. 26, 2020
$ / shares
shares
Jun. 05, 2015
item
$ / shares
shares
Mar. 31, 2021
USD ($)
shares
Mar. 31, 2020
USD ($)
shares
Dec. 31, 2020
Jul. 25, 2020
shares
May 31, 2013
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Weighted average remaining contractual life       6 years   3 years 7 months 6 days    
Share price | $ / shares     $ 17.31          
Options exercised       0 0      
Stock options expense | $       $ 114,000 $ 0      
Shares Under Options - Granted     800,000          
Common stock trade share price | $ / shares     $ 25.00          
Annual installments | item     3          
Exercisable period       10 years        
Common stock trading days       30 days        
Mahbod Nia, CEO [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Share price | $ / shares $ 15.79              
Shares Under Options - Granted 950,000              
Three Equal Annual Installment [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Shares Under Options - Granted     400,000          
Common Stock Trades [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Shares Under Options - Granted     400,000          
2013 Incentive Stock Plan [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Reserved stocks for issuance               4,600,000
MAG Partners [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Shares Under Options - Granted   157,505            
MAG Partners [Member] | Maximum [Member] | Common Class At $14.39 [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Number of shares authorized             230,000  
Share price issued | $ / shares   $ 14.39            
MAG Partners [Member] | Maximum [Member] | Common Class At $20.00 [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Share price | $ / shares   $ 20.00            
Number of shares authorized   100,000            
Share price issued | $ / shares   $ 20.00