Note 19 - Plant Consolidation (Details Textual)			12 Months Ended
	Mar. 18, 2015 USD ($) ft²	Jul. 16, 2014	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Restructuring Charges			$ 420,000	$ 1,756,000	$ 1,556,000
Number of Properties in Close Proximity		2
Selling, General and Administrative Expense			24,105,000	24,008,000	23,847,000
Gain (Loss) on Disposition of Property Plant Equipment			$ (2,000)	24,000	84,000
Restructuring Charges [Member]
Restructuring Charges				1,669,000	1,385,000
Selling, General and Administrative Expense				36,000	82,000
Gain (Loss) on Disposition of Property Plant Equipment				$ 51,000	$ 89,000
Newburyport, Massachusetts Facility [Member]
Area of Real Estate Property | ft²	137,000
Restructuring Charges	$ 2,100,000
Payments for Restructuring	2,000,000
Restructuring and Related Cost, Expected Annual Cost Savings Amount	1,000,000
Newburyport, Massachusetts Facility [Member] | Employee Severance Payments and Relocation Costs [Member]
Restructuring and Related Cost, Expected Cost	180,000
Newburyport, Massachusetts Facility [Member] | Moving and Vacating Expense [Member]
Restructuring and Related Cost, Expected Cost	1,500,000
Newburyport, Massachusetts Facility [Member] | Lease Termination [Member]
Restructuring and Related Cost, Expected Cost	$ 360,000