Annual report pursuant to Section 13 and 15(d)

Document and Entity Information

v3.8.0.1
Document and Entity Information - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2017
Jan. 31, 2018
Jun. 30, 2017
Entity Information [Line Items]      
Entity Registrant Name CORPORATE OFFICE PROPERTIES TRUST    
Entity Central Index Key 0000860546    
Document Type 10-K    
Document Period End Date Dec. 31, 2017    
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     $ 3,500.0
Entity Common Stock, Shares Outstanding   101,283,508  
Document Fiscal Year Focus 2017    
Document Fiscal Period Focus FY    
Corporate Office Properties, L.P. [Member]      
Entity Information [Line Items]      
Entity Registrant Name CORPORATE OFFICE PROPERTIES, L.P.    
Entity Central Index Key 0001577966    
Document Type 10-K    
Document Period End Date Dec. 31, 2017    
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 Non-accelerated Filer    
Entity Public Float     $ 108.9
Document Fiscal Year Focus 2017    
Document Fiscal Period Focus FY