Annual report pursuant to Section 13 and 15(d)

Document and Entity Information

v2.4.1.9
Document and Entity Information (USD $)
In Millions, except Share data, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Jan. 30, 2015
Jun. 30, 2014
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, 2014    
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     $ 1,600.0dei_EntityPublicFloat
Entity Common Stock, Shares Outstanding   93,414,408dei_EntityCommonStockSharesOutstanding  
Document Fiscal Year Focus 2014    
Document Fiscal Period Focus FY    
Corporate Office Properties, L.P.      
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, 2014    
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     $ 99.5dei_EntityPublicFloat
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
Document Fiscal Year Focus 2014    
Document Fiscal Period Focus FY