PREFERRED STOCK AND TEMPORARY EQUITY - Narrative (Details) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)	50,000,000
Preferred stock, par value (in dollars per share)	$ 0.001
Series A Preferred
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares issued (in shares)	419,859	419,859
Preferred stock, shares outstanding (in shares)	419,859	419,859
Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)	10,000,000
Preferred stock, shares issued (in shares)	3,826,055	3,604,827
Preferred stock, shares outstanding (in shares)	3,826,055	3,604,827
Series B1 Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)	17,000,000
Preferred stock, shares issued (in shares)	9,028,085	10,057,597
Preferred stock, shares outstanding (in shares)	9,028,085	10,057,597
Series C Preferred
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)	44,000	44,000
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0