Quarterly report pursuant to Section 13 or 15(d)

Significant Accounting Policies (Narrative) (Details)

v3.20.2
Significant Accounting Policies (Narrative) (Details) - USD ($)
 3 Months Ended 6 Months Ended 12 Months Ended
Jul. 13, 2020
Jul. 01, 2020
Jan. 01, 2019
Jun. 30, 2020
Dec. 31, 2019
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2019
Dec. 31, 2017
Mar. 31, 2020
Jan. 03, 2020
Mar. 31, 2019
Dec. 31, 2018
Significant Accounting Policies [Line Items]                          
Capitalized development and construction salaries and other related costs       $ 400,000   $ 600,000 $ 900,000 $ 1,100,000          
Maximum period after cessation of major construction activity that projects are considered complete             1 year            
Threshold of investment value for discontinuation of equity method accounting       0     $ 0            
Amortization of deferred financing costs       1,060,000   1,168,000 2,084,000 2,357,000          
Leasing personnel costs       663,000   $ 542,000 1,701,000 $ 1,284,000          
Deferred tax asset       $ 12,300,000     12,300,000   $ 5,300,000        
Income taxes, material adjustment amount             $ 0            
Common stock, shares outstanding       90,596,723 90,595,176   90,596,723       90,595,197    
Common units outstanding       9,586,528 9,612,064 9,976,344 9,586,528 9,976,344   9,518,638 9,488,794 10,009,355 10,229,349
LTIP units outstanding       2,659,518 1,826,331 1,826,331 2,659,518 1,826,331   3,094,324 1,949,601 1,826,331 1,707,106
Distributions payable, record date         Jan. 03, 2020   Jul. 13, 2020            
Distributions payable, approved date         Dec. 17, 2019                
Common stock dividends and common unit distributions per share         $ 0.20                
Stock compensation expense       $ 2,439,000   $ 2,191,000 $ 4,969,000 $ 4,071,000          
Distributions payable, pay date         Jan. 10, 2020   Jul. 01, 2020            
Increase (decrease) to valuation allowance                 $ (5,300,000)        
Federal income tax rate             21.00%            
Write off of unamortized deferred financing costs       0   0              
Gain from extinguishment of debt, net       0   588,000 $ 0 1,899,000          
Net income (loss)       (32,934,000)   (20,329,000) (70,778,000) 255,265,000          
Accounting Standards Update 2017-12 [Member]                          
Significant Accounting Policies [Line Items]                          
Net income (loss)     $ 400,000                    
Subsequent Event [Member]                          
Significant Accounting Policies [Line Items]                          
Common stock, shares outstanding 90,711,019                        
Common units outstanding 9,395,496                        
LTIP units outstanding 2,850,550                        
Common stock dividends and common unit distributions per share   $ 0.20                      
Dividends paid $ 20,600,000                        
Mack-Cali Realty LP [Member]                          
Significant Accounting Policies [Line Items]                          
Gain from extinguishment of debt, net           588,000   1,899,000          
Net income (loss)       $ (32,934,000)   $ (20,329,000) $ (70,778,000) $ 255,265,000          
LTIP value         $ 400,000                
Dividends paid         18,100,000                
Common Units [Member] | Mack-Cali Realty LP [Member] | Limited Partner Common Unitholders [Member]                          
Significant Accounting Policies [Line Items]                          
Dividends paid         $ 1,900,000