COMMITMENTS AND CONTINGENCIES (Details)	1 Months Ended	6 Months Ended
	Sep. 30, 2018 USD ($)	Jun. 30, 2021 USD ($) property officer	Dec. 31, 2020 USD ($)	Jun. 30, 2020 USD ($)
Commitment and Contingencies [Line Items]
Outstanding loan commitments to fund loans		$ 61,100,000
Purchase commitment, percentage of interest acquired		100.00%
Purchase commitment, number of properties acquired | property		1
Purchase commitment, purchase price committed		$ 2,900,000
Property escrow deposits		150,000
Future obligations under leases to fund tenant improvements and other future construction obligation		8,000,000.0
Restricted cash		$ 9,804,000	$ 10,013,000	$ 10,960,000
Employment agreements | Executive Officers
Commitment and Contingencies [Line Items]
Number of officers covered under employment agreement | officer		1
Multiplier used for the calculation of payments in the event of death of employee		2
Multiplier used for the calculation of payments in the event of disability to employee		1
Restricted Cash For Tenant Improvement Allowance
Commitment and Contingencies [Line Items]
Restricted cash		$ 2,500,000
City and County of San Francisco Real Property Transfer Tax Case | Pending Litigation
Commitment and Contingencies [Line Items]
Refund sought for penalties, interest and legal fees paid for real property transfer tax	$ 11,800,000