COPT Defense Properties Annual report pursuant to Section 13 and 15(d)

Annual report pursuant to Section 13 and 15(d)

Cover Page

Cover Page - USD ($) $ in Millions	12 Months Ended
Cover Page - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Jan. 28, 2020	Jun. 30, 2019
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2019
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
Entity Shell Company	false
Entity Public Float				$ 2,600.0
Entity Common Stock, Shares Outstanding			112,082,315
Entity Central Index Key	0000860546
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Documents Incorporated by Reference [Text Block]	This report also includes separate sections under Part II, Item 9A. Controls and Procedures and separate Exhibit 31 and Exhibit 32 certifications for each of COPT and COPLP to establish that the Chief Executive Officer and the Chief Financial Officer of each entity have made the requisite certifications and that COPT and COPLP are compliant with Rule 13a-15 and Rule 15d-14 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and 18 U.S.C. §1350.
Corporate Office Properties, L.P
Entity Information [Line Items]
Document Type	10-K
Document Period End Date	Dec. 31, 2019
Entity File Number	333-189188
Entity Registrant Name	Corporate Office Properties, L.P.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	23-2930022
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float				$ 27.7
Entity Central Index Key	0001577966
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Common Units \| Corporate Office Properties, L.P
Entity Information [Line Items]
Percentage ownership in operating partnership	98.70%	98.80%