Quarterly report pursuant to Section 13 or 15(d)

Equity (Details)

v3.3.0.814
Equity (Details) - USD ($)
$ / shares in Units, $ in Millions
 9 Months Ended
Sep. 30, 2015
Sep. 30, 2014
Class of Stock [Line Items]    
Number of operating partnerships units converted into common shares (in units) 160,160 117,149
Common Stock Issued to Public Under At-the-Market Program    
Class of Stock [Line Items]    
Shares issued to the public (in units/ shares) 890,241  
Weighted average price per share of stock issued $ 30.29  
Net proceeds of stock issuance $ 26.6  
Commission costs 0.4  
Common Shares    
Class of Stock [Line Items]    
Remaining capacity under ATM Plan $ 84.0  
Corporate Office Properties, L.P. | Common Shares    
Class of Stock [Line Items]    
Shares issued to the public (in units/ shares) 890,241