INCOME TAXES - Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Allowance for doubtful accounts	$ 250	$ 212
Accruals and reserves	1,768	1,902
Other	218	399
Total deferred tax assets	2,236	2,513
Deferred tax liabilities:
Property, plant, and equipment	6,375	5,926
Other	5	3
Total deferred tax liabilities	6,380	5,929
Valuation Allowance	0	0
Net deferred tax asset/(liability)	$ (4,144)	$ (3,416)