BACKGROUND AND ORGANIZATION - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Net loss	$ (30,976)	$ (26,743)	$ (26,152)	$ (27,532)	$ (57,719)	$ (53,684)
Net cash used in operations					(40,312)	$ (45,018)
Cash and cash equivalents	$ 166,925				$ 166,925		$ 156,720