COMMON STOCK - Common Stock Issued, Net of Issuance Costs (Details) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended		6 Months Ended
	Aug. 20, 2021	Dec. 04, 2020	Apr. 14, 2017	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Net proceeds from common stock						$ 24,541	$ 77,863
2020 Lincoln Park PA
Maximum aggregate offering price		$ 100,000
Period for financing from common stock		36 months
Number of common stock issued				0	1,200,000	0	5,000,000.0
Net proceeds from common stock					$ 5,700		$ 30,600
Threshold average sale price per share of common stock		$ 6.15
Registered share available for future sales		16,000,000.0
2020 Purchase Agreement with Lincoln Park | Maximum
Percentage of common stock issuable		19.99%
2020 Purchase Agreement with Lincoln Park | Lincoln Park
Minimum percentage considered for not to sale common stock		9.99%
ATM Offering Agreement
Number of common stock issued				4,400,000		11,800,000	9,300,000
Net proceeds from common stock	$ 50,000			$ 9,000		$ 24,500	$ 47,300
Gross proceeds from issuance of common stock						$ 27,600
ATM Offering Agreement | Cantor Fitzgerald & Co | Maximum
Sales commission percentage			2.50%