STOCKHOLDERS' EQUITY - Redeemable Convertible Preferred Stock, IPO, Public Offering and ATM Offering Narrative (Details) - USD ($)				3 Months Ended	9 Months Ended
	Jun. 05, 2020	May 18, 2020	May 13, 2019	Sep. 30, 2020	Sep. 30, 2020
Subsidiary, Sale of Stock [Line Items]
Payments of stock issuance costs				$ 200,000	$ 400,000
IPO
Subsidiary, Sale of Stock [Line Items]
Shares converted (in shares)			14,641,997
2020 Follow-on Offering
Subsidiary, Sale of Stock [Line Items]
Shares sold (in shares)		12,650,000
Shares sold, par value (USD per share)		$ 4.75
Net proceeds on offering		$ 55,900,000
At-the-Market Offering
Subsidiary, Sale of Stock [Line Items]
Shares sold (in shares)				1,253,597	1,658,861
Net proceeds on offering				$ 6,900,000	$ 9,000,000.0
At-the-Market Offering | Maximum
Subsidiary, Sale of Stock [Line Items]
Net proceeds on offering	$ 35,000,000