Quarterly report pursuant to Section 13 or 15(d)

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

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Mack-Cali Realty Corporation Stockholders' Equity And Mack-Cali Realty, L.P.'s Partners' Capital (Schedule Of Stock Option Plans) (Details) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 9 Months Ended
Jun. 05, 2015
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Jun. 30, 2019
Dec. 31, 2018
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]              
Shares Under Options - Outstanding, beginning balance   800,000 800,000        
Shares Under Options - Granted 800,000 172,495          
Shares Under Options - Outstanding, ending balance   972,495 800,000 972,495 800,000    
Shares Under Options - Options exercisable   972,495 800,000 972,495 800,000    
Shares Under Options - Available for grant   717,155 751,936 717,155 751,936    
Weighted Average Exercise Price - Outstanding, beginning balance   $ 17.31 $ 17.31        
Weighted Average Exercise Price - Granted   14.39          
Weighted Average Exercise Price - Outstanding, ending balance   $ 16.79 $ 17.31 $ 16.79 $ 17.31    
Aggregate intrinsic value     $ 3,480   $ 3,480 $ 4,784  
2013 Incentive Stock Plan [Member]              
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]              
Shares Under Options - Outstanding, beginning balance       800,000 800,000    
Shares Under Options - Granted       172,495      
Shares Under Options - Outstanding, ending balance   972,495 800,000 972,495 800,000    
Shares Under Options - Options exercisable   972,495 800,000 972,495 800,000    
Shares Under Options - Available for grant   717,155 751,936 717,155 751,936    
Weighted Average Exercise Price - Outstanding, beginning balance       $ 17.31 $ 17.31    
Weighted Average Exercise Price - Granted       14.39      
Weighted Average Exercise Price - Outstanding, ending balance   $ 16.79 $ 17.31 16.79 $ 17.31    
Aggregate intrinsic value     $ 3,480   $ 3,480   $ 1,824
Outstanding stock option price     $ 17.31   $ 17.31    
Minimum [Member] | 2013 Incentive Stock Plan [Member]              
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]              
Outstanding stock option price   14.39   14.39      
Maximum [Member] | 2013 Incentive Stock Plan [Member]              
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]              
Outstanding stock option price   $ 17.31   $ 17.31