CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Net sales	$ 112,035	$ 108,920	$ 108,994
Cost of goods sold	77,210	73,753	75,593
Gross profit	34,825	35,167	33,401
Selling, general and administrative expense	19,590	19,593	19,430
Operating income	15,235	15,574	13,971
Interest income	1,929	390	50
Income before income taxes	17,164	15,964	14,021
Provision for income taxes	3,961	5,507	4,903
Net income	$ 13,203	$ 10,457	$ 9,118
Basic and diluted earnings per common share	$ 1.06	$ 0.84	$ 0.73
Cash dividends per share	$ 0.20	$ 0.20	$ 0.20
Basic and diluted weighted average shares outstanding	12,423	12,416	12,408