REAL ESTATE EQUITY SECURITIES - Additional Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) investment	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) investment shares	Jun. 30, 2019 USD ($)
Debt Securities, Available-for-sale [Line Items]
Number of investments in equity securities | investment	3		3
Purchase price			$ 10,964	$ 24,076
Dividend income from real estate equity securities	$ 900	$ 300	$ 2,400	$ 2,100
Plymouth Industrial REIT, Inc.
Debt Securities, Available-for-sale [Line Items]
Number of shares purchased (in shares) | shares			609,623
Payments to acquire investments			$ 7,300
Plymouth Industrial REIT, Inc. | Common Stock
Debt Securities, Available-for-sale [Line Items]
Issuance of common stock (in shares) | shares			617,316
Purchase price			$ 11,000
Franklin Street Properties Corp.
Debt Securities, Available-for-sale [Line Items]
Number of shares purchased (in shares) | shares			2,437,292
Payments to acquire investments			$ 14,000