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 9 Months Ended 12 Months Ended
Jun. 05, 2015
item
$ / shares
shares
Sep. 30, 2019
USD ($)
Sep. 30, 2018
USD ($)
Sep. 30, 2019
USD ($)
shares
Sep. 30, 2018
USD ($)
shares
Dec. 31, 2018
May 31, 2013
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Weighted average remaining contractual life       5 years 8 months 12 days   6 years 4 months 24 days  
Share price | $ / shares $ 17.31            
Options exercised       0 0    
Stock options expense | $   $ 0 $ 0 $ 0 $ 193,000    
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      
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