INVESTMENT IN AN UNCONSOLIDATED ENTITY - Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Balance Sheets [Abstract]
Real estate, net	$ 1,922,659		$ 1,922,659			$ 2,028,943
Total assets	2,350,573		2,350,573			2,504,325
Notes payable, net	1,593,822		1,593,822			1,388,365
Total liabilities	1,740,810		1,740,810			1,559,566
Total equity	522,318	$ 884,935	522,318	$ 884,935	$ 520,152	898,036	$ 911,206	$ 985,310
Income Statement [Abstract]
Total revenues	73,061	75,503	221,650	229,176
Company’s share of net income (loss)	1,595	588	4,945	(1,408)
SREIT
Balance Sheets [Abstract]
Real estate, net	1,521,812		1,521,812			1,318,527
Total assets	1,574,268		1,574,268			1,383,372
Notes payable, net	642,466		642,466			480,352
Total liabilities	709,475		709,475			546,486
Total equity	864,793		864,793			$ 836,886
Income Statement [Abstract]
Total revenues	40,603	36,623	114,922	108,993
Net income (loss)	2,179	2,144	14,446	(12,830)
Company’s share of net income (loss)	540	$ 588	3,890	(3,504)
Equity in gain for dilution of an unconsolidated entity	1,100		1,100	2,100
SREIT | Purchase and Sales Agreement
Income Statement [Abstract]
Equity in gain for dilution of an unconsolidated entity	$ 1,100		$ 1,100	$ 2,100