Quarterly report pursuant to Section 13 or 15(d)

Mack-Cali Realty Corporation Stockholders' Equity And Mack-Cali Realty, L.P.'s Partners' Capital (Restricted Stock Awards And Performance Share Units) (Narrative) (Details)

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Mack-Cali Realty Corporation Stockholders' Equity And Mack-Cali Realty, L.P.'s Partners' Capital (Restricted Stock Awards And Performance Share Units) (Narrative) (Details) - USD ($)
6 Months Ended
Jun. 05, 2018
Jun. 05, 2015
Jun. 30, 2020
Mar. 31, 2020
Dec. 31, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Unvested stock outstanding     17,076 42,690 42,690 26,136 66,321 67,289
Performance period     3 years          
Restricted Stock [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Unvested stock outstanding     17,076          
Restricted Stock [Member] | 2013 Incentive Stock Plan [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Shares granted   37,550.54            
Performance period     3 years          
Restricted Stock [Member] | Minimum [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Stock compensation vesting period     1 year          
Restricted Stock [Member] | Maximum [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Stock compensation vesting period     7 years          
Unvested Restricted Stock [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Unvested stock outstanding     17,076     26,136    
Total Stockholder Return Based Awards [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Total unrecognized compensation cost     $ 0          
Performance Shares [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Unvested performance shares     0          
Total unrecognized compensation cost     $ 0          
Performance Shares [Member] | 2013 Incentive Stock Plan [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Shares granted   112,651.64            
Performance period     3 years          
Performance Shares [Member] | 2013 Incentive Stock Plan [Member] | Three Years Period Award [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Percentage of shares vested 100.00%              
Performance Shares [Member] | Minimum [Member] | 2013 Incentive Stock Plan [Member] | Three Years Period Award [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Percentage of shares vested     0.00%          
Performance Shares [Member] | Maximum [Member] | 2013 Incentive Stock Plan [Member] | Three Years Period Award [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Percentage of shares vested     150.00%