SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Redeemable Common Stock and Reclassification (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended		127 Months Ended
	Mar. 20, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Dec. 31, 2019
Summary of Significant Accounting Policies [Line Items]
Redemptions of common stock	$ 8,600	$ 356	$ 2,568	$ 824	$ 5,107	$ 286,200
Number of shares non-redeemable due to limitation (in shares)				5,973,671
Other liabilities		19,472		$ 19,472		19,472	$ 19,801
Remaining authorized repurchase amount		6		6		6
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			$ 3		$ 6
Number of shares non-redeemable due to limitation				60,300
Common Stock | Share Redemption Program
Summary of Significant Accounting Policies [Line Items]
Redemptions of common stock				$ 800