REAL ESTATE HELD FOR INVESTMENT - Highest Tenant Industry Concentrations- Greater than 10% of Annual Base Rent (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) tenant
Concentration Risk [Line Items]
Number of tenants | tenant	243
Annualized Base Rent | $	$ 21,053
Percentage of Annualized Base Rent	35.80%
Insurance
Concentration Risk [Line Items]
Number of tenants | tenant	25
Annualized Base Rent | $	$ 7,180
Percentage of Annualized Base Rent	12.20%
Computer Systems Design
Concentration Risk [Line Items]
Number of tenants | tenant	25
Annualized Base Rent | $	$ 6,949
Percentage of Annualized Base Rent	11.80%
Health Care and Social Assistance
Concentration Risk [Line Items]
Number of tenants | tenant	16
Annualized Base Rent | $	$ 6,924
Percentage of Annualized Base Rent	11.80%