Annual report pursuant to Section 13 and 15(d)

Equity - COPT and Subsidiaries (Details)

v3.3.1.900
Equity - COPT and Subsidiaries (Details) - USD ($)
 1 Months Ended 12 Months Ended
Jun. 16, 2014
Jul. 15, 2013
Nov. 30, 2014
Oct. 31, 2012
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Preferred Stock              
Number of shares issued         7,431,667    
Aggregate liquidation preference         $ 199,083,000 $ 199,083,000  
Stock redeemed or called during period value           50,000,000 $ 84,750,000
Common Shares              
Shares issued to the public     5,520,000        
Per share value of common and preferred shares issued to the public (in dollars per share)     $ 27.30        
Net proceeds from issue of shares after underwriter discounts but before offering expenses     $ 148,900,000     $ 148,666,000 $ 117,961,000
Number of common shares for each converted common unit (in shares)         1    
Number of operating partnerships units converted into common shares (in units)         160,160 140,149 311,343
Dividends declared per common share         $ 1.1000 $ 1.10 $ 1.10
Common Stock Issued to Public Under At-the-Market Program [Member]              
Common Shares              
Shares issued to the public   1,500,000.0     890,241   1,500,000
At-market-stock, offering program established, aggregate value       $ 150,000,000.0      
Issuance of stock, weighted average price per share         $ 30.29    
Payments of stock issuance costs   $ 600,000     $ 400,000    
At-market stock, offering program established, remaining capacity         84,000,000    
Share Price   $ 26.05          
Proceeds from Issuance of Common Stock, Net of Issuance Costs   $ 38,500,000     $ 26,600,000    
Preferred Shares [Member]              
Preferred Stock              
Number of preferred shares authorized         25,000,000    
Number of preferred shares of beneficial interest authorized (in dollars per share)         $ 0.01    
Series H [Member]              
Preferred Stock              
Annual dividend yield 7.50%            
Preferred stock, redemption price per share $ 25            
Stock redeemed or called during period value $ 50,000,000            
Issuance costs associated with redeemed preferred shares $ 1,800,000            
Series K [Member]              
Preferred Stock              
Number of shares issued         531,667    
Aggregate liquidation preference         $ 26,583,000    
Annual dividend yield         5.60%    
Annual dividend per share (in dollars per share)         $ 2.80000    
Number of common shares to be issued on conversion of each preferred share         0.8163    
Series L [Member]              
Preferred Stock              
Number of shares issued         6,900,000    
Aggregate liquidation preference         $ 172,500,000    
Annual dividend yield         7.375%    
Annual dividend per share (in dollars per share)         $ 1.84375