Quarterly report pursuant to Section 13 or 15(d)

Significant Accounting Policies (Narrative) (Details)

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Significant Accounting Policies (Narrative) (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Significant Accounting Policies [Line Items]        
Capitalized development and construction salaries and other related costs $ 600 $ 400 $ 1,200 $ 900
Maximum period after cessation of major construction activity that projects are considered complete     1 year  
Gain (Loss) from extinguishment of debt, net     $ (46,735)  
Mack-Cali Realty LP [Member]        
Significant Accounting Policies [Line Items]        
Gain (Loss) from extinguishment of debt, net $ (46,735)   $ (46,735)