COPT Defense Properties Quarterly report pursuant to Section 13 or 15(d)

Properties, Net - 2020 Development Activities (Details) ft² in Thousands	Mar. 31, 2020 ft² property
Newly developed properties placed in service
Real Estate [Line Items]
Area of real estate property (in sqft or acres) \| ft²	230
Number of real estate properties \| property	1
Properties under development or contractually committed for construction
Real Estate [Line Items]
Area of real estate property (in sqft or acres) \| ft²	2,200
Number of real estate properties \| property	13
Properties under or approved for redevelopment partially-operational
Real Estate [Line Items]
Area of real estate property (in sqft or acres) \| ft²	106
Number of real estate properties \| property	1