LEASES - Summary of components of net lease cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Leases [Abstract]
Operating lease cost	$ 751	$ 505	$ 2,264	$ 1,111
Finance lease cost	6	6	17	10
Variable lease cost	58	23	161	66
Total lease cost	$ 815	$ 534	$ 2,442	$ 1,187