ORGANIZATION AND NATURE OF BUSINESS; BASIS OF PRESENTATION; PRINCIPLES OF CONSOLIDATION (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Mar. 27, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accumulated deficit	$ (607,239)				$ (570,668)				$ (607,239)	$ (570,668)
Net loss	(14,609)	$ (15,896)	$ (18,523)	$ (13,465)	(22,803)	$ (8,986)	$ (21,674)	$ (24,239)	(62,493)	(77,702)	$ (78,208)
Net cash used in operating activities									(48,728)	(47,323)	$ (50,394)
Debt Instrument [Line Items]
Cash and cash equivalents and investments	$ 45,600				$ 63,600				45,600	$ 63,600
Decrease in cash and cash equivalents and investments									$ (18,000)
2.50% Convertible Notes due 2023 | Convertible Notes
Debt Instrument [Line Items]
Interest rate												2.50%