PROPERTY, PLANT & EQUIPMENT, & FINANCE LEASE (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property, plant and equipment - gross	$ 247,240	$ 247,223
Less accumulated depreciation	187,587	180,562
Net property, plant and equipment	59,653	66,661
Finance lease	30,550	30,405
Less finance lease accumulated amortization	1,558	13
Net property, plant and equipment, and finance lease	88,645	97,053
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment - gross	3,053	2,998
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment - gross	84,262	84,005
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment - gross	153,592	154,016
Property under construction
Property, Plant and Equipment [Line Items]
Property, plant and equipment - gross	$ 6,333	$ 6,204