Plant Consolidation (Details)		12 Months Ended
	Mar. 18, 2015 USD ($) ft²	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Restructuring Costs
Employee severance payments		$ 196,000	$ 247,000
Relocation costs		1,204,000	857,000
Lease Termination Costs		356,000
Workforce training costs			373,000
Plant infrastructure costs			79,000
Total restructuring costs		1,756,000	1,556,000
Selling, general and administrative expenses		24,008,000	23,847,000	$ 23,605,000
Restructuring costs		1,756,000	1,556,000
(Gain) loss on sales of property, plant and equipment		(24,000)	(84,000)	$ 11,000
Restructuring Charges
Restructuring Costs
Selling, general and administrative expenses		36,000	82,000
Restructuring costs		1,669,000	1,385,000
(Gain) loss on sales of property, plant and equipment		51,000	89,000
Grand Rapids Michigan Facility
Restructuring Costs
Employee severance payments			237,000
Relocation costs			356,000
Workforce training costs			373,000
Plant infrastructure costs			79,000
Total restructuring costs			1,045,000
Rancho Dominguez California Facility
Restructuring Costs
Employee severance payments		18,000	10,000
Relocation costs		66,000	501,000
Total restructuring costs		84,000	$ 511,000
Newburyport Massachusetts facility
Plant Consolidation
Restructuring charges	$ 2,100,000
Cash charges	2,000,000
Annual cost savings	$ 1,000,000
Restructuring Costs
Employee severance payments		178,000
Relocation costs		1,138,000
Lease Termination Costs		356,000
Total restructuring costs		$ 1,672,000
Acquired commercial building, Square foot | ft²	137,000
Employee severance payments | Newburyport Massachusetts facility
Plant Consolidation
Restructuring charges	$ 180,000
Moving and vacating expenses | Newburyport Massachusetts facility
Plant Consolidation
Restructuring charges	1,500,000
Lease Termination | Newburyport Massachusetts facility
Plant Consolidation
Restructuring charges	$ 360,000