INVESTMENT IN AN UNCONSOLIDATED ENTITY - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		2 Months Ended		3 Months Ended		9 Months Ended
	Jul. 19, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Aug. 21, 2019
Schedule of Equity Method Investments [Line Items]
Investment in an unconsolidated entity		$ 232,649		$ 232,649		$ 232,649		$ 253,371
Equity in income (loss) of an unconsolidated entity		2,600		(588)	$ 2,556	1,408	$ 2,556
SREIT
Schedule of Equity Method Investments [Line Items]
Equity in income (loss) of an unconsolidated entity			$ 2,556	(588)		3,504
Purchase and Sales Agreement | SREIT
Schedule of Equity Method Investments [Line Items]
Investment in an unconsolidated entity		$ 232,600		232,600		232,600
Equity in gain for dilution of an unconsolidated entity						2,100
Investment income, dividends				$ 7,400		$ 19,300
REIT Properties III | Purchase and Sales Agreement
Schedule of Equity Method Investments [Line Items]
Units acquired (in units)	307,953,999
Units acquired	$ 271,000
Units acquired (in dollars per unit)	$ 0.88
Ownership percentage	33.30%	27.40%		27.40%		27.40%			31.30%
Units disposed (in units)									18,392,100
Units disposed									$ 16,200
Units held (in units)		289,561,899		289,561,899		289,561,899
Investment in an unconsolidated entity		$ 238,900		$ 238,900		$ 238,900
Units, closing price (in dollars per unit)		$ 0.83		$ 0.83		$ 0.83