Annual report pursuant to Section 13 and 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)
 12 Months Ended
Jun. 05, 2015
item
$ / shares
shares
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
May 31, 2013
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Weighted average remaining contractual life   5 years 4 months 24 days 6 years 4 months 24 days    
Share price | $ / shares $ 17.31        
Proceeds from stock options exercised | $   $ 0 $ 0 $ 0  
Stock options expense | $   $ 0 $ 193,000 $ 464,000  
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