REDEEMABLE PREFERRED STOCK - Series A Preferred Stock Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended		60 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Jan. 31, 2020
Class of Stock [Line Items]
Redeemable preferred stock deemed dividends	$ 90			$ 87			$ 253	$ 300
Reclassification of Series A Preferred Stock from temporary equity to permanent equity							$ 34,552	$ 27,434	$ 134,700
Registration Statement
Class of Stock [Line Items]
Warrant right to purchase a share of common stock (in shares)										0.25
Series A Preferred Stock
Class of Stock [Line Items]
Reclassification of Series A Preferred Stock from temporary equity to permanent equity	$ 13,828	$ 12,481	$ 8,243	$ 10,747	$ 9,739	$ 6,948
Series A Preferred Stock | Registration Statement
Class of Stock [Line Items]
Preferred stock, par value (in usd per share)										$ 0.001
Preferred stock, stated value (in usd per share)										$ 25.00