COMMITMENTS AND CONTINGENCIES - Additional Information (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) ft² option	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Commitments And Contingencies [Line Items]
Operating lease (including related operating costs)	$ 301,000	$ 298,000
Canada
Commitments And Contingencies [Line Items]
Office space, square foot | ft²	31,100
Lease term	2 years
Renewal option | option	1
Renewal term	3 years
Monthly rent	$ 12,600
Related operating expenses	12,300
Operating lease (including related operating costs)	$ 300,000
Rent expense under ASC 842		300,000
Rent expense under ASC 840			$ 300,000
Massachusetts
Commitments And Contingencies [Line Items]
Lease term	4 months
Monthly rent	$ 7,900
Rent expense under ASC 842	100,000
Pennsylvania
Commitments And Contingencies [Line Items]
Monthly rent	13,500
Rent expense under ASC 842	$ 200,000	$ 100,000