REAL ESTATE INVESTMENTS - Capitalized Construction Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Internal direct construction costs capitalized related to development of properties and land holdings	$ 8,366	$ 7,431	$ 6,964
Capitalized interest	4,600	3,200	3,600
Development
Property, Plant and Equipment [Line Items]
Internal direct construction costs capitalized related to development of properties and land holdings	4,802	3,047	3,185
Redevelopment
Property, Plant and Equipment [Line Items]
Internal direct construction costs capitalized related to development of properties and land holdings	543	775	968
Tenant Improvements
Property, Plant and Equipment [Line Items]
Internal direct construction costs capitalized related to development of properties and land holdings	$ 3,021	$ 3,609	$ 2,811