LEASES - Right-of-use assets and lease liabilities relating to operating and finance leases (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Right-of-use assets:
Operating leases	$ 5,759	$ 6,518
Finance leases	2,780
Total right-of-use assets	8,539	6,518
Lease liabilities:
Operating lease	5,759	6,518
Finance lease	2,373
Total lease liabilities	$ 8,132	$ 6,518
Weighted Average Remaining Lease Term [Abstract]
Operating leases	4 years 8 months 12 days	6 years 2 months 12 days
Finance leases	11 years 4 months 24 days	0 years
Weighted Average Discount Rate [Abstract]
Operating leases	2.60%	3.10%
Finance leases	2.50%