ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP - Summary of Properties (Details)	Dec. 31, 2020 ft² property
Real Estate Properties [Line Items]
Number of Properties | property	82
Area of real estate property | ft²	13,852,464
Office properties
Real Estate Properties [Line Items]
Number of Properties | property	73
Area of real estate property | ft²	12,470,257
Mixed-use properties
Real Estate Properties [Line Items]
Number of Properties | property	5
Area of real estate property | ft²	942,334
Core Properties
Real Estate Properties [Line Items]
Number of Properties | property	78
Area of real estate property | ft²	13,412,591
Development property
Real Estate Properties [Line Items]
Number of Properties | property	1
Area of real estate property | ft²	205,803
Redevelopment properties
Real Estate Properties [Line Items]
Number of Properties | property	3
Area of real estate property | ft²	234,070