LEASES - Right-of-Use Assets and Lease Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Right of use assets
Operating Lease - ROU	$ 6,868	$ 5,838
Finance Leases - ROU	2,412	2,572
Total right-of-use assets	9,280	8,410
Operating leases liabilities - current	2,278	2,178
Finance leases liabilities - current	165	159
Total lease liabilities, current	2,443	2,337
Operating leases liabilities - non-current	4,644	3,607
Finance leases liabilities - non-current	2,345	2,472
Total lease liabilities, non-current	$ 6,989	$ 6,079
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Total right-of-use assets	Total right-of-use assets
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Total right-of-use assets	Total right-of-use assets
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Total lease liabilities, current	Total lease liabilities, current
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Total lease liabilities, current	Total lease liabilities, current
Operating Lease, Liability, Statement of Financial Position [Extensible Enumeration]	Total lease liabilities, non-current	Total lease liabilities, non-current
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Total lease liabilities, non-current	Total lease liabilities, non-current