Quarterly report pursuant to Section 13 or 15(d)

Redeemable Noncontrolling Interests (Narrative) (Details)

v3.20.2
Redeemable Noncontrolling Interests (Narrative) (Details)
 3 Months Ended 9 Months Ended 12 Months Ended
Jun. 30, 2019
USD ($)
Jun. 28, 2019
USD ($)
Jun. 26, 2019
USD ($)
property
Mar. 10, 2017
USD ($)
Feb. 28, 2017
USD ($)
$ / shares
shares
Feb. 27, 2017
USD ($)
Feb. 03, 2017
USD ($)
$ / shares
shares
Sep. 30, 2020
USD ($)
$ / shares
Sep. 30, 2019
USD ($)
$ / shares
Sep. 30, 2020
USD ($)
$ / shares
Sep. 30, 2019
USD ($)
$ / shares
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Apr. 30, 2017
shares
Redeemable Noncontrolling Interest [Line Items]                            
General and administrative               $ 28,945,000 $ 12,571,000 $ 62,005,000 $ 42,836,000      
Expiration period                   10 years        
Payment for borrowings                   $ 364,000,000 398,000,000      
Minimum [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Percentage of interest in venture               20.00%   20.00%        
Maximum [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Percentage of interest in venture               85.00%   85.00%        
Mack-Cali Realty LP [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
General and administrative               $ 28,945,000 $ 12,571,000 $ 62,005,000 $ 42,836,000      
Common unit distribution per unit declared | $ / shares               $ 0 $ 0.20 $ 0.40 $ 0.60      
Payment for borrowings                   $ 364,000,000 $ 398,000,000      
Series A Units [Member] | Mack-Cali Realty LP [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Preferred units shares issued | shares             42,800              
Preferred unit annual rate             3.50%              
Percentage of interest in venture             37.50%              
Preferred unit in operating partnership             $ 1,000              
Convertible preferred units | shares             28.15              
Expiration period             5 years              
Shares that may be converted to common units | shares             1,204,820              
Common unit distribution per unit declared | $ / shares             $ 35.52              
Series A-1 Units [Member] | Mack-Cali Realty LP [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Preferred units shares issued | shares         9,213                 91
Preferred unit annual rate         3.50%                  
Percentage of interest in venture         13.80%                  
Preferred unit in operating partnership         $ 1,000                  
Convertible preferred units | shares         27.936                  
Expiration period         5 years         5 years        
Shares that may be converted to common units | shares         257,375                  
Common unit distribution per unit declared | $ / shares         $ 35.80                  
Monaco [Member] | Series A-1 Units [Member] | Mack-Cali Realty LP [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Preferred units shares issued | shares         9,122                  
Investment Agreement [Member] | Minimum [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Incremental closing payments, Limited Partnership interest                         $ 105,000,000  
RRLP [Member] | Cash Flow From Operations [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Annual return on the equity value                   6.00%        
RRLP [Member] | Investment Agreement [Member] | Cash Flow From Capital Events, Distribution Four [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Capital base return                   5.00%        
RRLP [Member] | Credit Enhancement Note [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Maximum borrowing capacity               $ 50,000,000   $ 50,000,000        
Increased line of credit               25,000,000   $ 25,000,000        
Spread over LIBOR                   50.00%        
Rockpoint [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Estimated redemption value                   $ 480,000,000        
Rockpoint [Member] | Cash Flow From Operations [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Invested capital               400,000,000   400,000,000        
Rockpoint [Member] | Cash Flow From Capital Events, Distribution Five [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Invested capital               400,000,000   400,000,000        
Rockpoint [Member] | Cash Flow From Capital Events, Distribution Six [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Invested capital               $ 400,000,000   $ 400,000,000        
Rockpoint [Member] | Distribution One [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Purchase price   $ 173,500,000                        
Purchase price, less distributions   198,500,000                        
Rockpoint [Member] | Distribution Two [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Purchase price, less distributions   $ 1,500,000                        
Rockpoint [Member] | Preferred Units [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Pro rata distribution                   10.947%        
Rockpoint [Member] | Preferred Units [Member] | Cash Flow From Operations [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Pro rata distribution                   21.89%        
Rockpoint [Member] | Preferred Units [Member] | Cash Flow From Capital Events, Distribution Five [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Pro rata distribution                   21.89%        
Rockpoint [Member] | Investment Agreement [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Contributed equity value       $ 1,230,000,000                    
Incremental closing payments, Limited Partnership interest     $ 46,000,000 $ 150,000,000             $ 45,000,000      
Rockpoint [Member] | Investment Agreement [Member] | Maximum [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Contributed amount to obtain equity units           $ 300,000,000                
Rockpoint [Member] | Add On Investment Agreement [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Contributed amount to obtain equity units     $ 100,000,000                      
Number of properties in which additional interest was acquired during period | property     2                      
Right of first refusal to invest                   $ 100,000,000        
General and administrative                       $ 371,000    
Payment for borrowings $ 100,000,000                          
Rockpoint [Member] | Add On Investment Agreement [Member] | Maximum [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Contributed amount to obtain equity units                   $ 154,000,000        
Rockpoint [Member] | RRLP [Member] | Cash Flow From Operations [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Annual return                   6.00%        
Base return                   4.64%        
Rockpoint [Member] | RRLP [Member] | Cash Flow From Capital Events, Distribution Three [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Base return                   4.64%        
Rockpoint [Member] | RRLP [Member] | Cash Flow From Capital Events, Distribution Four [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Capital base return                   4.64%        
Rockpoint [Member] | RRLP [Member] | Cash Flow From Capital Events, Distribution Five [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Internal rate of return                   11.00%        
Rockpoint [Member] | RRLP [Member] | Cash Flow From Capital Events, Distribution Six [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Pro rata share                   50.00%        
Rockpoint [Member] | RRLP [Member] | Investment Agreement [Member] | Cash Flow From Operations [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Base return                   5.00%        
Rockpoint [Member] | RRLP [Member] | Investment Agreement [Member] | Cash Flow From Capital Events, Distribution Three [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Base return                   95.00%        
RRT [Member] | Preferred Units [Member] | Cash Flow From Operations [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Pro rata distribution                   2.65%        
RRT [Member] | Preferred Units [Member] | Cash Flow From Capital Events, Distribution Five [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Pro rata distribution                   2.65%        
RRT [Member] | Preferred Units [Member] | Cash Flow From Capital Events, Distribution Six [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Pro rata distribution                   1.325%        
RRT [Member] | Common Units [Member] | Cash Flow From Operations [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Pro rata distribution                   75.46%        
RRT [Member] | Common Units [Member] | Cash Flow From Capital Events, Distribution Five [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Pro rata distribution                   75.46%        
RRT [Member] | Common Units [Member] | Cash Flow From Capital Events, Distribution Six [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Pro rata distribution                   87.728%        
RRT [Member] | RRLP [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Loan-to-value ratio     65.00%                      
Equity capitalization percent                   10.00%        
RRT [Member] | RRLP [Member] | Cash Flow From Operations [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Base return                   95.36%        
RRT [Member] | RRLP [Member] | Cash Flow From Capital Events, Distribution Three [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Base return                   95.36%        
RRT [Member] | RRLP [Member] | Cash Flow From Capital Events, Distribution Four [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Capital base return                   95.36%        
RRT [Member] | RRLP [Member] | Investment Agreement [Member] | Cash Flow From Operations [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Base return                   95.00%        
RRT [Member] | RRLP [Member] | Investment Agreement [Member] | Cash Flow From Capital Events, Distribution Three [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Base return                   5.00%        
RRT [Member] | RRLP [Member] | Investment Agreement [Member] | Cash Flow From Capital Events, Distribution Four [Member]                            
Redeemable Noncontrolling Interest [Line Items]                            
Capital base return                   95.00%