Annual report pursuant to Section 13 and 15(d)

Equity - COPT and Subsidiaries (Details)

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Equity - COPT and Subsidiaries (Details) - USD ($)
 1 Months Ended 12 Months Ended
Nov. 30, 2018
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Common Shares        
Number of common shares for each converted common unit (in shares)   1 1 1
Number of operating partnerships units converted into common shares (in units)   8,054 14,009 105,039
Dividends declared per common share (in dollars per share)   $ 1.10 $ 1.10 $ 1.10
Preferred Shares        
Preferred Stock        
Number of preferred shares authorized   25,000,000    
Number of preferred shares of beneficial interest authorized (in dollars per share)   $ 0.01    
2018 ATM Program | Common Shares        
Common Shares        
At-market-stock, offering program established, aggregate value $ 300,000,000      
Shares issued to the public (in shares)   0    
Forward Equity Sale Agreement | Common Shares        
Common Shares        
Shares issued to the public (in shares)       1,600,000
Net proceeds from issuance of shares after underwriting discounts and commissions but before offering expenses       $ 46,500,000
Initial gross offering price per share (in dollars per share)       $ 31.00