Annual report pursuant to Section 13 and 15(d)

Noncontrolling Interests In Subsidiaries (Narrative) (Details)

v3.19.3.a.u2
Noncontrolling Interests In Subsidiaries (Narrative) (Details)
$ in Thousands
 3 Months Ended 12 Months Ended
Mar. 26, 2019
USD ($)
item
Jun. 05, 2015
shares
Mar. 31, 2019
USD ($)
property
shares
Dec. 31, 2019
USD ($)
property
item
shares
Dec. 31, 2018
USD ($)
item
Dec. 31, 2017
USD ($)
Mar. 25, 2019
Noncontrolling Interest [Line Items]              
Number of common shares received upon redemption of common units | shares       1      
Rebalance of ownership percentage | $       $ 1,800      
Number of units | item       208 1,317    
Purchase price of property | $       $ 97,504 $ 112,511 $ 90,422  
Shares granted | shares   800,000          
Participation Rights [Member]              
Noncontrolling Interest [Line Items]              
Number of properties | property       2      
Excess net cash flow remaining after the distribution to the Company       50.00%      
Internal rate of return       10.00%      
Mack-Cali Realty LP [Member]              
Noncontrolling Interest [Line Items]              
Purchase price of property | $       $ 97,504 $ 112,511    
Mack-Cali Realty LP [Member]              
Noncontrolling Interest [Line Items]              
Percentage of noncontrolling interest       9.60% 10.20%    
Future Developments [Member] | Participation Rights [Member]              
Noncontrolling Interest [Line Items]              
Number of properties | property       1      
Disposal Group, Not Discontinued Operations [Member]              
Noncontrolling Interest [Line Items]              
Number of properties disposed | property       2      
Proceeds from sale of properties | $       $ 6,600      
Redemption of common units, shares | shares       301,638      
Number of units | item       377      
Disposal Group, Not Discontinued Operations [Member] | Flex Portfolio [Member]              
Noncontrolling Interest [Line Items]              
Number of properties disposed | property     2        
Proceeds from sale of properties | $     $ 6,600 $ 7,800      
Redemption of common units, shares | shares     301,638 364,280      
XS Hotel Urban Renewal Associates LLC [Member]              
Noncontrolling Interest [Line Items]              
Percentage of interest in venture 100.00%           0.90%
Number of units | item 372            
Percentage of additional interest acquired 10.00%            
Purchase price of property | $ $ 5,000            
XS Hotel Urban Renewal Associates LLC, Residence Inn [Member]              
Noncontrolling Interest [Line Items]              
Number of units | item 164            
XS Hotel Urban Renewal Associates LLC, Marriott Envue [Member]              
Noncontrolling Interest [Line Items]              
Number of units | item 208            
Messr DeMarco, CEO [Member]              
Noncontrolling Interest [Line Items]              
Shares granted | shares       625,000      
AO LTIP Units Award [Member] | Messr DeMarco, CEO [Member]              
Noncontrolling Interest [Line Items]              
Shares granted | shares       625,000