Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Net sales	$ 100,008	$ 96,273	$ 305,790	$ 300,663
Cost of sales	62,969	57,626	189,047	183,609
Gross margin	37,039	38,647	116,743	117,054
Selling, engineering and administration	24,628	24,705	74,272	75,384
Operating earnings	12,411	13,942	42,471	41,670
Interest expense, net	242	213	567	711
Earnings before income taxes	12,169	13,729	41,904	40,959
Provision for income taxes	4,194	4,937	14,566	14,777
Net earnings	$ 7,975	$ 8,792	$ 27,338	$ 26,182
Earnings per share:
Basic (in dollars per share)	$ 0.28	$ 0.30	$ 0.94	$ 0.91
Diluted (in dollars per share)	0.27	0.30	0.94	0.90
Dividends declared per common share (in dollars per share)	$ 0.13	$ 0.115	$ 0.360	$ 0.315
Shares used in computation of earnings per share:
Basic (in shares)	28,939,292	28,898,526	28,939,940	28,879,307
Impact of dilutive securities (in shares)	178,756	162,306	173,468	160,500
Diluted (in shares)	29,118,048	29,060,832	29,113,408	29,039,807