SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Real Estate Sale and Estimated Useful Lives) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) property	Dec. 31, 2018 USD ($) property	Dec. 31, 2017 USD ($) property
Property, Plant and Equipment [Line Items]
Gain on sale of real estate | $	$ 4,178	$ 0	$ 0
Buildings | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	25 years
Buildings | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	40 years
Building improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	10 years
Building improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	25 years
Tenant improvements
Property, Plant and Equipment [Line Items]
Estimated useful lives	Shorter of lease term or expected useful life
Tenant origination and absorption costs
Property, Plant and Equipment [Line Items]
Estimated useful lives	Remaining term of related leases, including below-market renewal periods
Real estate subsidies & tax abatements
Property, Plant and Equipment [Line Items]
Estimated useful lives	Remaining term of agreement
Furniture, fixtures & equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years
Furniture, fixtures & equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	12 years
Disposed of by Sale
Property, Plant and Equipment [Line Items]
Number of properties disposed | property		0	0
Disposed of by Sale | Office Building
Property, Plant and Equipment [Line Items]
Number of properties disposed | property	1	0
Gain on sale of real estate | $	$ 4,200