Organization (Details) - Jun. 30, 2018 ft² in Millions	a	MW	ft²	Property
Operating Properties
Investments in real estate
Number of real estate properties				159
Area of real estate property (in square feet or acres) | ft²			17.7
Operating Properties | Office Properties
Investments in real estate
Number of real estate properties				143
Operating Properties | Single-tenant data centers
Investments in real estate
Number of real estate properties				16
Properties under, or contractually committed for, construction or approved for redevelopment
Investments in real estate
Number of real estate properties				9
Area of real estate property (in square feet or acres) | ft²			1.0
Properties under, or contractually committed for, construction or approved for redevelopment | Office Properties
Investments in real estate
Number of real estate properties				5
Properties under, or contractually committed for, construction or approved for redevelopment | Single-tenant data centers
Investments in real estate
Number of real estate properties				4
Properties under, or contractually committed for, construction or approved for redevelopment | Partially operational properties
Investments in real estate
Number of real estate properties				1
Land controlled for future development
Investments in real estate
Area of real estate property (in square feet or acres)	1,000		12.3
Other Land
Investments in real estate
Area of real estate property (in square feet or acres) | a	150
Operating wholesale data centers
Investments in real estate
Critical load (in megawatts) | MW		19.25
GI-COPT | Operating Properties | Single-tenant data centers
Investments in real estate
Number of real estate properties				6