Annual report pursuant to Section 13 and 15(d)

Mack-Cali Realty Corporation Stockholders' Equity And Mack-Cali Realty, L.P.'s Partners' Capital (Long-Term Incentive Plan Awards) (Narrative) (Details)

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Mack-Cali Realty Corporation Stockholders' Equity And Mack-Cali Realty, L.P.'s Partners' Capital (Long-Term Incentive Plan Awards) (Narrative) (Details) - USD ($)
 12 Months Ended
Mar. 22, 2019
Apr. 20, 2018
Apr. 04, 2017
Mar. 08, 2016
Jun. 05, 2015
Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares granted         800,000  
Performance Shares [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Total unrecognized compensation cost           $ 0
2016 LTIP Awards [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Dividends paid, percent representing common unit of limited partnership interest           10.00%
Dividends paid, percent payable upon vesting of LTIP Unit           90.00%
Total unrecognized compensation cost           $ 12,300,000
Total unrecognized compensation cost, period of recognition           2 years 2 months 12 days
Shares forfeited and cancelled           354,422
2016 TBV LTIP Units [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares granted           79,266
2016 OPP [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Performance period           3 years
TSR percent           50.00%
2016 OPP [Member] | Performance Shares [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Performance period           3 years
2016 PBV LTIP Units [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares granted           11,155
2017 OPP [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Performance period           3 years
TSR percent           36.00%
2017 PBV LTIP Units [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares granted           390,654
2017 TBV LTIP Units [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares granted           80,434
2018 OPP [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Performance period           3 years
TSR percent           36.00%
2018 PBV LTIP Units [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares granted           629,252
2018 TBV LTIP Units [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares granted           193,217
2019 OPP [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Performance period           3 years
TSR percent           36.00%
Messieur Rudin, Messieur DeMarco, And Messieur Tycher [Member] | 2016 LTIP Awards [Member] | Time-Based Award [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Percent of the award       25.00%    
Performance period           3 years
Messieur Rudin, Messieur DeMarco, And Messieur Tycher [Member] | 2016 LTIP Awards [Member] | Performance Shares [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Remaining percent of the award       75.00%    
Messieur Rudin, Messieur DeMarco, And Messieur Tycher [Member] | 2017 LTIP Awards [Member] | Time-Based Award [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Percent of the award     25.00%      
Messieur Rudin, Messieur DeMarco, And Messieur Tycher [Member] | 2017 LTIP Awards [Member] | Performance Shares [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Remaining percent of the award     75.00%      
Messieur Rudin, Messieur DeMarco, And Messieur Tycher [Member] | 2017 TBV LTIP Units [Member] | Time-Based Award [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Performance period           3 years
Other Executive Officers [Member] | 2016 LTIP Awards [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Percent of the award       40.00%    
Remaining percent of the award       60.00%    
Other Executive Officers [Member] | 2017 LTIP Awards [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Percent of the award     40.00%      
Remaining percent of the award     60.00%      
Other Executive Officers [Member] | 2018 LTIP Awards [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Percent of the award   50.00%        
Remaining percent of the award   50.00%        
Messieur DeMarco And Messieur Tycher [Member] | 2018 LTIP Awards [Member] | Time-Based Award [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Percent of the award   25.00%        
Performance period           3 years
Messieur DeMarco And Messieur Tycher [Member] | 2018 LTIP Awards [Member] | Performance Shares [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Remaining percent of the award   75.00%        
Messr DeMarco, CEO [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares granted           625,000
Messr DeMarco, CEO [Member] | 2019 LTIP Awards [Member] | Time-Based Award [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Percent of the award 25.00%          
Messr DeMarco, CEO [Member] | 2019 LTIP Awards [Member] | Performance Shares [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Remaining percent of the award           75.00%
Messieur Tycher, Smetana, Wagner, Cardoso, And Hilton [Member] | 2019 TBV LTIP Units [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Percent of the award           50.00%
Messieur Tycher, Smetana, Wagner, Cardoso, And Hilton [Member] | 2019 PBV LTIP Units [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Remaining percent of the award           50.00%
Messieur DeBari [Member] | 2019 LTIP Awards [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Percent of the award           100.00%