SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Redeemable Common Stock and Reclassification (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended		130 Months Ended
	Mar. 20, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Dec. 31, 2019
Summary of Significant Accounting Policies [Line Items]
Redemptions of common stock	$ 8,600	$ 6	$ 2,326	$ 830	$ 7,433	$ 286,300
Number of shares non-redeemable due to limitation (in shares)				5,938,443
Other liabilities		19,745		$ 19,745		19,745	$ 19,801
Unfulfilled Redemption Request
Summary of Significant Accounting Policies [Line Items]
Other liabilities		$ 300		300		$ 300	$ 800
Common Stock
Summary of Significant Accounting Policies [Line Items]
Redemptions of common stock			$ 2		$ 8
Number of shares non-redeemable due to limitation				60,000
Common Stock | Share Redemption Program
Summary of Significant Accounting Policies [Line Items]
Redemptions of common stock				$ 800