Consolidated Condensed Statements of Operations (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Income Statement [Abstract]
Net sales	$ 88,341	$ 81,974	$ 160,149	$ 158,207
Cost of sales	58,495	51,773	105,266	99,142
Gross margin	29,846	30,201	54,883	59,065
Selling, engineering and administration	19,686	18,846	39,998	37,522
Operating earnings	10,160	11,355	14,885	21,543
Interest expense, net	332	238	580	443
Earnings before income taxes	9,828	11,117	14,305	21,100
Provision for income taxes	3,547	3,675	5,117	7,409
Net earnings	$ 6,281	$ 7,442	$ 9,188	$ 13,691
Earnings per share:
Basic	$ 0.44	$ 0.52	$ 0.64	$ 0.94
Diluted	$ 0.44	$ 0.52	$ 0.64	$ 0.94
Dividends declared – Common stock	$ 0.17	$ 0.16	$ 0.34	$ 0.32
Shares used in computation of earnings per share:
Basic	14,365,536	14,234,900	14,345,143	14,527,328
Impact of dilutive securities	65,463	72,332	81,806	68,785
Diluted	14,430,999	14,307,232	14,426,949	14,596,113