COMMITMENTS AND CONTINGENCIES - Leases expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating lease, weighted average remaining lease term	1 year 9 months 18 days
Operating lease costs	$ 49	$ 52
Variable lease costs	7	15
Total lease costs	$ 56	$ 67
Minimum
Operating lease liability discount rates (in percent)	3.99%
Maximum
Operating lease liability discount rates (in percent)	8.95%