Annual report pursuant to Section 13 and 15(d)

Equity - COPLP and Subsidiaries (Details)

v3.10.0.1
Equity - COPLP and Subsidiaries (Details) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 12 Months Ended
Jun. 27, 2017
Jan. 21, 2017
Dec. 31, 2016
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Preferred Stock            
Stock redeemed or called during period value         $ 172,500 $ 26,583
Preferred units in COPLP       $ 8,800 $ 8,800  
Common Shares            
Number of common shares for each converted common unit (in shares)       1    
Number of operating partnerships units converted into common shares (in units)       1,904,615 339,513 87,000
Redemption of preferred shares       $ 339    
Dividends declared per common share (in dollars per share)       $ 1.1 $ 1.10 $ 1.10
2016 ATM Program [Member]            
Common Shares            
Shares issued to the public       992,000 591,000 3,700,000
Issuance of stock, weighted average price per share (in dollars per share)     $ 29.56 $ 30.46 $ 33.84 $ 29.56
Payments of stock issuance costs       $ 500 $ 300 $ 900
Net proceeds from issuance of shares after underwriting discounts and commissions but before offering expenses       $ 29,800 $ 19,700 $ 109,100
Common Shares [Member] | 2016 ATM Program [Member]            
Common Shares            
Shares issued to the public     3,700,000 992,000 591,000  
Issuance of stock, weighted average price per share (in dollars per share)     $ 29.56 $ 30.46 $ 33.84 $ 29.56
Payments of stock issuance costs     $ 900 $ 500 $ 300  
Net proceeds from issuance of shares after underwriting discounts and commissions but before offering expenses     109,100 $ 29,800 $ 19,700  
Common Shares [Member] | Forward Equity Sale Agreement [Member]            
Common Shares            
Shares issued to the public       5,900,000 1,700,000  
Net proceeds from issuance of shares after underwriting discounts and commissions but before offering expenses       $ 172,500 $ 50,000  
Series K Preferred Shares [Member]            
Preferred Stock            
Annual dividend yield   5.60%        
Issuance costs associated with redeemed preferred shares     17      
Series L [Member]            
Preferred Stock            
Annual dividend yield 7.375%          
Issuance costs associated with redeemed preferred shares         6,800  
Corporate Office Properties, L.P. [Member]            
Preferred Stock            
Stock redeemed or called during period value         $ 172,500 $ 26,583
Common Shares            
Number of common shares for each converted common unit (in shares)       1    
Number of operating partnerships units converted into common shares (in units)       1,900,000 339,513.000 87,000
Redemption of preferred shares       $ 339    
Dividends declared per common share (in dollars per share)       $ 1.1 $ 1.10 $ 1.10
Corporate Office Properties, L.P. [Member] | Common Shares [Member]            
Common Shares            
Stock redeemed or called during period (in units/ shares)       13,377    
Redemption of preferred shares       $ 339    
Corporate Office Properties, L.P. [Member] | Common Units [Member]            
Common Shares            
Percentage ownership in operating partnership       98.80% 96.90%  
Stock redeemed or called during period (in units/ shares)       13,377    
Redemption of preferred shares       $ 339    
Corporate Office Properties, L.P. [Member] | Conversion of Series I preferred units [Member]            
Preferred Stock            
Annual dividend yield       7.50%    
Limited partners' capital account, units issued       352,000    
Preferred units in COPLP       $ 8,800    
Preferred stock, liquidation preference per share       $ 25    
Annual cumulative preferred return increment frequency       5 years    
Common units conversion basis units issuable       0.5    
Corporate Office Properties, L.P. [Member] | Series K Preferred Shares [Member]            
Preferred Stock            
Annual dividend yield   5.60%        
Preferred stock, redemption price per share (in dollars per share)   $ 50.00        
Stock redeemed or called during period value   $ 26,600        
Issuance costs associated with redeemed preferred shares     $ 17      
Corporate Office Properties, L.P. [Member] | Series L [Member]            
Preferred Stock            
Annual dividend yield 7.375%          
Preferred stock, redemption price per share (in dollars per share) $ 25.00          
Stock redeemed or called during period value $ 172,500          
Issuance costs associated with redeemed preferred shares         $ 6,800