Summary of Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Total gross value	$ 134,435	$ 133,569
Less accumulated depreciation	(85,114)	(83,274)
Total net value	49,321	50,295
Land
Property, Plant and Equipment [Line Items]
Total gross value	2,458	2,458
Buildings and improvements
Property, Plant and Equipment [Line Items]
Total gross value	$ 16,678	15,515
Buildings and improvements | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment estimated useful life	10 years
Buildings and improvements | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment estimated useful life	30 years
Machinery and equipment
Property, Plant and Equipment [Line Items]
Total gross value	$ 107,722	102,146
Machinery and equipment | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment estimated useful life	3 years
Machinery and equipment | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment estimated useful life	15 years
Office furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Total gross value	$ 4,925	5,016
Office furniture, fixtures and equipment | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment estimated useful life	3 years
Office furniture, fixtures and equipment | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment estimated useful life	10 years
Automotive equipment
Property, Plant and Equipment [Line Items]
Total gross value	$ 735	387
Automotive equipment | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment estimated useful life	3 years
Automotive equipment | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment estimated useful life	6 years
Construction in progress
Property, Plant and Equipment [Line Items]
Total gross value	$ 1,917	$ 8,047