Quarterly report pursuant to Section 13 or 15(d)

Mack-Cali Realty Corporation Stockholders' Equity And Mack-Cali Realty, L.P.'s Partners' Capital (Deferred Stock Compensation Plan For Directors) (Narrative) (Details)

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Mack-Cali Realty Corporation Stockholders' Equity And Mack-Cali Realty, L.P.'s Partners' Capital (Deferred Stock Compensation Plan For Directors) (Narrative) (Details) - shares
 3 Months Ended 9 Months Ended
Jun. 12, 2020
Jun. 12, 2019
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Dec. 31, 2020
Mack-Cali Realty Corporation Stockholders' Equity And Mack-Cali Realty, L.P.'s Partners' Capital [Abstract]              
Maximum percentage of retainer fee that directors may defer         100.00%    
Deferred stock units earned     5,113 5,952 13,494 15,663  
Deferred stock units converted 61,277 193,949          
Deferred stock units outstanding     32,659   32,659   17,854