Statements of Consolidated Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Net sales	$ 336,634	$ 354,666	$ 388,185
Cost of products sold	227,220	251,214	267,237
GROSS PROFIT	109,414	103,452	120,948
Costs and expenses
Selling	31,799	30,593	35,655
General and administrative	42,057	36,878	42,563
Research and engineering	14,025	14,879	16,302
Other operating expenses - net	54	8,753	5,190
Total costs and expenses	87,935	91,103	99,710
OPERATING INCOME	21,479	12,349	21,238
Other income (expense)
Interest income	291	391	483
Interest expense	(844)	(565)	(658)
Other income (expense)	27	(469)	347
Total other income (expense)	(526)	(643)	172
INCOME BEFORE INCOME TAXES	20,953	11,706	21,410
Income taxes	5,698	5,031	8,549
NET INCOME	$ 15,255	$ 6,675	$ 12,861
BASIC EARNINGS PER SHARE
Net income	$ 2.95	$ 1.25	$ 2.39
DILUTED EARNINGS PER SHARE
Net income	2.95	1.24	2.39
Cash dividends declared per share	$ 0.80	$ 0.80	$ 0.80
Weighted-average number of shares outstanding - basic	5,166	5,350	5,377
Weighted-average number of shares outstanding - diluted	5,178	5,366	5,382