LEASES - Components of lease expenses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Operating lease cost
Total operating lease expense	$ 1,072	$ 419	$ 2,415	$ 1,181
Finance lease cost:
Total amortization of leased assets	29	16	78	44
Interest on lease liabilities	11	5	31	14
Total net lease cost	$ 1,112	$ 440	$ 2,524	$ 1,239