STOCKHOLDERS' EQUITY - AT MARKET ISSUANCE SALES AGREEMENT (Details) - USD ($)			3 Months Ended				9 Months Ended
	Sep. 04, 2020	May 18, 2018	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2020
At Market Issuance Sales Agreements [Line Items]
Net cash proceeds from issuance of common stock after deducting sales commissions and other offering costs			$ 3,389,000	$ 686,000	$ 8,959,000	$ 101,000
2018 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)							3,496,616
Net cash proceeds from issuance of common stock after deducting sales commissions and other offering costs							$ 4,075,000
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%