Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
Net sales	$ 104,176	$ 103,820	$ 205,782	$ 204,390
Cost of sales	63,122	64,424	126,078	125,983
Gross margin	41,054	39,396	79,704	78,407
Selling, engineering and administration	24,463	24,474	49,644	50,679
Operating earnings	16,591	14,922	30,060	27,728
Interest expense, net	147	228	325	498
Earnings before income taxes	16,444	14,694	29,735	27,230
Provision for income taxes	5,830	5,294	10,372	9,840
Net earnings	$ 10,614	$ 9,400	$ 19,363	$ 17,390
Earnings per share:
Basic (in dollars per share)	$ 0.37	$ 0.33	$ 0.67	$ 0.60
Diluted (in dollars per share)	0.36	0.32	0.67	0.60
Dividends declared per common share (in dollars per share)	$ 0.115	$ 0.1	$ 0.23	$ 0.20
Shares used in computation of earnings per share:
Basic (in shares)	28,938,451	28,887,078	28,938,851	28,868,794
Impact of dilutive securities (in shares)	159,369	164,331	170,824	159,597
Diluted (in shares)	29,097,820	29,051,409	29,109,675	29,028,391