Condensed Consolidated Statements of Earnings (unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Condensed Consolidated Statements of Earnings (unaudited) [Abstract]
Net sales	$ 84,651	$ 76,203
Cost of sales	60,419	55,045
Gross margin	24,232	21,158
Operating expenses:
Selling expenses	4,287	4,087
Research and development expenses	838	776
General and administrative expenses	3,242	2,620
Operating expenses	8,367	7,483
Earnings from operations	15,865	13,675
Other expenses (income):
Interest income	(52)	(7)
Interest expense	1	3
Other, net	53	(9)
Earnings before income tax expense	15,863	13,688
Income tax expense	4,975	4,420
Net earnings	$ 10,888	$ 9,268
Net earnings per common share - basic (in dollars per share)	$ 0.37	$ 0.32
Net earnings per common share - diluted (in dollars per share)	$ 0.36	$ 0.31