STOCKHOLDERS' EQUITY - AT MARKET ISSUANCE SALES AGREEMENT (Details) - USD ($)		3 Months Ended
	Sep. 04, 2020	Mar. 31, 2021	Mar. 31, 2020
At Market Issuance Sales Agreements [Line Items]
Net cash proceeds from issuance of common stock after deducting sales commissions and other offering costs		$ 16,234,000	$ 686,000
2020 Sales Agreement
At Market Issuance Sales Agreements [Line Items]
Aggregate offering price of common stock	$ 100,000,000
Maximum commission rate (as a percent)	3.00%
Issuance of common stock in connection with at market offering (in shares)		7,948,505
Net cash proceeds from issuance of common stock after deducting sales commissions and other offering costs		$ 16,234,000