Annual report pursuant to Section 13 and 15(d)

Cover Page

v3.22.0.1
Cover Page - USD ($)
$ in Billions
 12 Months Ended
Dec. 31, 2021
Feb. 07, 2022
Jun. 30, 2021
Cover [Abstract]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2021    
Current Fiscal Year End Date --12-31    
Document Transition Report false    
Entity File Number 1-14023    
Entity Registrant Name CORPORATE OFFICE PROPERTIES TRUST    
Entity Incorporation, State or Country Code MD    
Entity Tax Identification Number 23-2947217    
Entity Address, Address Line One 6711 Columbia Gateway Drive    
Entity Address, Address Line Two Suite 300    
Entity Address, City or Town Columbia    
Entity Address, State or Province MD    
Entity Address, Postal Zip Code 21046    
City Area Code 443    
Local Phone Number 285-5400    
Title of 12(b) Security Common Shares of beneficial interest, $0.01 par value    
Trading Symbol OFC    
Security Exchange Name NYSE    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag true    
Entity Shell Company false    
Entity Public Float     $ 2.8
Entity Common Stock, Shares Outstanding   112,319,982  
Documents Incorporated by Reference Portions of the proxy statement of Corporate Office Properties Trust for its 2022 Annual Meeting of Shareholders to be filed within 120 days after the end of the fiscal year covered by this Form 10-K are incorporated by reference into Part III of this Form 10-K.    
Entity Central Index Key 0000860546    
Amendment Flag false    
Document Fiscal Year Focus 2021    
Document Fiscal Period Focus FY