INCOME TAXES - Deferred income tax assets and liabilities (Details 3) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Allowance for doubtful accounts	$ 213	$ 181
Accruals and reserves	1,963	1,673
Other	811	644
Total deferred tax assets	2,987	2,498
Deferred tax liabilities:
Property, plant, and equipment	4,686	3,579
Other	1	0
Total deferred tax liabilities	4,687	3,579
Valuation Allowance	0	(44)
Net deferred tax asset/(liability)	$ (1,700)	$ (1,125)