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

Organization (Details) - Jun. 30, 2015 ft² in Millions	a ft² Property MW
Debt in default of payment terms \| Northern Virginia \| Wholly owned subsidiary
Investments in real estate
Number of real estate properties \| Property	2
Operating office properties
Investments in real estate
Number of real estate properties \| Property	179
Square footage of real estate properties (in square feet)	18.0
Office properties under, or contractually committed for, construction or approved for redevelopment
Investments in real estate
Number of real estate properties \| Property	12
Square footage of real estate properties (in square feet)	1.3
Land controlled for future development
Investments in real estate
Square footage of real estate properties (in square feet) \| a	1,450
Developable square feet	17.7
Partially operational, wholesale data center
Investments in real estate
The expected stabilization critical load after completion of development (in megawatts) \| MW	19.25