Annual report pursuant to Section 13 and 15(d)

Document and Entity Information

v2.4.0.6
Document and Entity Information (USD $)
In Billions, except Share data, unless otherwise specified
 12 Months Ended
Dec. 31, 2011
Jan. 27, 2012
Jun. 30, 2011
Document and Entity Information      
Entity Registrant Name CORPORATE OFFICE PROPERTIES TRUST    
Entity Central Index Key 0000860546    
Document Type 10-K    
Document Period End Date Dec. 31, 2011    
Amendment Flag false    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Filer Category Large Accelerated Filer    
Entity Public Float     $ 2.2
Entity Common Stock, Shares Outstanding   72,019,987  
Document Fiscal Year Focus 2011    
Document Fiscal Period Focus FY