Annual report pursuant to Section 13 and 15(d)

Noncontrolling Interests In Subsidiaries (Narrative) (Details)

v3.20.4
Noncontrolling Interests In Subsidiaries (Narrative) (Details)
$ in Millions
 12 Months Ended
Jun. 05, 2015
shares
Dec. 31, 2020
USD ($)
property
shares
Dec. 31, 2019
shares
Noncontrolling Interest [Line Items]      
Number of common shares received upon redemption of common units   1  
Rebalance of ownership percentage | $   $ 2.6  
Shares granted 800,000    
Exercisable period   10 years  
Participation Rights [Member]      
Noncontrolling Interest [Line Items]      
Number of properties | property   1  
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]      
Percentage of noncontrolling interest   9.60% 9.60%
Future Developments [Member] | Participation Rights [Member]      
Noncontrolling Interest [Line Items]      
Number of properties | property   1  
Disposal Group, Not Discontinued Operations [Member] | Flex Portfolio [Member]      
Noncontrolling Interest [Line Items]      
Redemption of common units, shares   138,615  
Value of units redeemed | $   $ 2.7  
AO LTIP Units Award [Member]      
Noncontrolling Interest [Line Items]      
Exercisable period   10 years  
AO LTIP Units Award [Member] | Messr DeMarco, CEO [Member]      
Noncontrolling Interest [Line Items]      
Shares granted   625,000 625,000