Consolidated Statements of Earnings - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidated Statements of Earnings [Abstract]
Net sales	$ 594,790	$ 553,204	$ 552,492
Cost of sales	405,781	372,343	384,395
Gross margin	189,009	180,861	168,097
Operating expenses:
Selling expenses	54,720	55,172	46,255
Research and development expenses	9,305	7,325	5,990
General and administrative expenses	27,729	27,526	21,896
Total operating expenses	91,754	90,023	74,141
Earnings from operations	97,255	90,838	93,956
Other expenses (income):
Interest income	(12)	(9)	(9)
Interest expense	7,544	7,265	6,593
Other, net	1,235	648	309
Earnings before income tax expense	88,488	82,934	87,063
Income tax (benefit)/expense	(1,583)	26,962	27,341
Net earnings	$ 90,071	$ 55,972	$ 59,722
Basic net earnings per common share (in dollars per share)	$ 2.83	$ 1.78	$ 1.92
Diluted net earnings per common share (in dollars per share)	$ 2.79	$ 1.75	$ 1.89