LEASES - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) ft² contract	Dec. 31, 2019 USD ($)	Jul. 31, 2020 USD ($) ft²	Feb. 28, 2019 ft²
Lessee, Lease, Description [Line Items]
Number of leases | contract	3
Minimum lease payments due	$ 10,624
Operating lease expense	$ 1,545
Rent expense		$ 415
Principal office, July 2020 lease
Lessee, Lease, Description [Line Items]
Lease term			7 years
Lease term, optional extension			5 years
Area leased | ft²			25,578
Minimum lease payments due			$ 18,751
Minimum lease payments due, lease portion not yet commenced			8,222
Letter of credit outstanding			$ 1,168
Principal office, February 2019 lease
Lessee, Lease, Description [Line Items]
Lease term, optional extension				3 years
Area leased | ft²				2,357
Office and laboratory, December 2020 lease
Lessee, Lease, Description [Line Items]
Lease term	11 years
Lease term, optional extension	5 years
Area leased | ft²	18,120
Minimum lease payments due	$ 21,373