Statements of Consolidated Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Net sales	$ 420,878	$ 378,212	$ 336,634
Cost of products sold	288,647	259,584	227,220
GROSS PROFIT	132,231	118,628	109,414
Costs and expenses
Selling	36,358	34,048	31,799
General and administrative	45,398	43,160	42,057
Research and engineering	15,107	14,327	14,025
Other operating expenses - net	2,434	985	54
Total costs and expenses	99,297	92,520	87,935
OPERATING INCOME	32,934	26,108	21,479
Other income (expense)
Interest income	486	430	291
Interest expense	(1,290)	(1,061)	(844)
Other income (expense)	458	329	27
Total other income (expense)	(346)	(302)	(526)
INCOME BEFORE INCOME TAXES	32,588	25,806	20,953
Income taxes	6,007	13,152	5,698
NET INCOME	$ 26,581	$ 12,654	$ 15,255
BASIC EARNINGS PER SHARE
Net income	$ 5.28	$ 2.48	$ 2.95
DILUTED EARNINGS PER SHARE
Net income	5.21	2.47	2.95
Cash dividends declared per share	$ 0.80	$ 0.80	$ 0.80
Weighted-average number of shares outstanding - basic	5,032	5,102	5,166
Weighted-average number of shares outstanding - diluted	5,107	5,133	5,178