Property, Plant and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	$ 67,859	$ 64,247
Less allowances for depreciation and amortization	45,535	43,405
Property, plant and equipment, net	22,324	20,842	$ 15,979
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	226	226
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	13,071	12,583
Building and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	10,116	10,084
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	32,761	30,728
Construction in progress, including internal-use capitalized software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	$ 11,685	$ 10,626