Annual report pursuant to Section 13 and 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
12 Months Ended
Jun. 12, 2020
Jun. 12, 2019
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
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     22,086 14,337 26,620
Deferred stock units converted 61,277 193,949      
Deferred stock units outstanding     17,854 59,899