Condensed Consolidated Statements of Earnings (unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Condensed Consolidated Statements of Earnings (unaudited) [Abstract]
Net sales	$ 85,995	$ 84,651
Cost of sales	62,780	60,419
Gross margin	23,215	24,232
Operating expenses:
Selling expenses	4,189	4,287
Research and development expenses	773	838
General and administrative expenses	4,898	3,242
Operating expenses	9,860	8,367
Earnings from operations	13,355	15,865
Other expenses (income):
Interest income	(46)	(52)
Interest expense	1	1
Other, net	28	53
Earnings before income tax expense	13,372	15,863
Income tax expense	4,478	4,975
Net earnings	$ 8,894	$ 10,888
Net earnings per common share - basic (in dollars per share)	$ 0.30	$ 0.37
Net earnings per common share - diluted (in dollars per share)	$ 0.29	$ 0.36