Condensed Consolidated Statements of Earnings (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Condensed Consolidated Statements of Earnings (unaudited) [Abstract]
Net sales	$ 138,509	$ 140,128	$ 412,444	$ 419,763
Cost of sales	93,853	96,954	278,515	291,592
Gross margin	44,656	43,174	133,929	128,171
Operating expenses:
Selling expenses	13,601	11,807	41,182	34,960
Research and development expenses	1,681	1,510	5,543	4,450
General and administrative expenses	6,428	6,935	20,957	17,027
Total operating expenses	21,710	20,252	67,682	56,437
Earnings from operations	22,946	22,922	66,247	71,734
Other expenses (income):
Interest income	(2)	(3)	(7)	(7)
Interest expense	1,790	1,617	5,538	5,092
Other, net	387	119	581	209
Earnings before income tax expense	20,771	21,189	60,135	66,440
Income tax expense	6,759	7,213	20,087	22,377
Net earnings	$ 14,012	$ 13,976	$ 40,048	$ 44,063
Net earnings per common share - basic (in dollars per share)	$ 0.44	$ 0.45	$ 1.27	$ 1.42
Net earnings per common share - diluted (in dollars per share)	$ 0.44	$ 0.44	$ 1.26	$ 1.40