Quarterly report pursuant to Section 13 or 15(d)

Document and Entity Information

v2.4.0.6
Document and Entity Information
9 Months Ended
Sep. 30, 2012
Oct. 18, 2012
Document and Entity Information [Abstract]    
Entity Registrant Name CORPORATE OFFICE PROPERTIES TRUST  
Entity Central Index Key 0000860546  
Document Type 10-Q  
Document Period End Date Sep. 30, 2012  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Entity Common Stock, Shares Outstanding   80,793,776
Document Fiscal Year Focus 2012  
Document Fiscal Period Focus Q3