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 6 Months Ended 12 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2019
Dec. 31, 2019
Mar. 31, 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 - Outstanding, ending balance 800,000 800,000 800,000 800,000      
Shares Under Options - Options exercisable 800,000 800,000 800,000 800,000      
Shares Under Options - Available for grant 225,469 750,000 225,469 750,000      
Weighted Average Exercise Price - Outstanding, beginning balance $ 17.31 $ 17.31          
Weighted Average Exercise Price - Outstanding, ending balance $ 17.31 $ 17.31 $ 17.31 $ 17.31      
Aggregate intrinsic value   $ 4,784   $ 4,784   $ 3,912  
2013 Incentive Stock Plan [Member]              
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]              
Shares Under Options - Outstanding, beginning balance     800,000 800,000 800,000    
Shares Under Options - Outstanding, ending balance 800,000 800,000 800,000 800,000 800,000    
Shares Under Options - Options exercisable 800,000 800,000 800,000 800,000      
Shares Under Options - Available for grant 225,469 750,000 225,469 750,000      
Weighted Average Exercise Price - Outstanding, beginning balance     $ 17.31 $ 17.31 $ 17.31    
Weighted Average Exercise Price - Outstanding, ending balance $ 17.31 $ 17.31 17.31 $ 17.31 17.31    
Aggregate intrinsic value   $ 4,784   $ 4,784     $ 1,824
Outstanding stock option price $ 17.31 $ 17.31 $ 17.31 $ 17.31 $ 17.31