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 ($)
$ in Millions
 12 Months Ended
Mar. 22, 2019
Apr. 20, 2018
Apr. 04, 2017
Mar. 08, 2016
Jun. 05, 2015
Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Performance period           3 years
Shares granted         800,000  
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           $ 8.0
Total unrecognized compensation cost, period of recognition           2 years 3 months 18 days
2016 TBV LTIP Units [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares granted           68,205
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           3,718
2017 LTIP Awards [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares forfeited and cancelled           369,924
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           10,264
2017 TBV LTIP Units [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares granted           70,772
2018 LTIP Awards [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares forfeited and cancelled           102,639
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           542,651
2018 TBV LTIP Units [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares granted           177,179
2019 LTIP Awards [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares forfeited and cancelled           175,570
2019 TBV LTIP Units [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares granted           140,995
2019 PBV LTIP Units [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares granted           249,058
2019 OPP [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Performance period           3 years
TSR percent           36.00%
2020 OPP [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Performance period           3 years
TSR percent           36.00%
2020 PBV LTIP Units [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares granted           720,314
2020 LTIP Awards [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Performance period           3 years
Shares forfeited and cancelled           567,254
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 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
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] | 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%
Messr DeBari [Member] | 2019 LTIP Awards [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Percent of the award           100.00%