Property, Plant and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 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	$ 22,193	$ 21,649	$ 20,984	20,842	$ 20,988	$ 19,088	$ 17,643	$ 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