BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Reclassifications (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash and cash equivalents	$ 75,192	$ 372,093	$ 75,192	$ 372,093	$ 23,801
Other assets	9,922		9,922		$ 9,222
Decrease to net cash provided by (used in) operating activities			(5,241)	(24,937)
Asset management and other fees to related parties	(2,376)	(3,195)	(5,021)	(7,797)
Non-segment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Expense reimbursements to related parties	615	542	1,427	1,189
Reportable segments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Expense reimbursements to related parties	$ 998	551	$ 1,680	1,188
Revision of Prior Period, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash and cash equivalents		(1,572)		(1,572)		$ (272)
Other assets		1,572		1,572		$ 272
Decrease to net cash provided by (used in) operating activities				1,300
Revision of Prior Period, Adjustment | Reclassification, Type, One
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Asset management and other fees to related parties		542		1,189
Revision of Prior Period, Adjustment | Reclassification, Type, Two
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Asset management and other fees to related parties		551		1,188
Revision of Prior Period, Adjustment | Non-segment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Expense reimbursements to related parties		542		1,189
Revision of Prior Period, Adjustment | Reportable segments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Expense reimbursements to related parties		$ 551		$ 1,188