Consolidated Statements of Earnings - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Net sales	$ 643,679	$ 594,790	$ 553,204
Cost of sales	439,427	405,781	372,343
Gross margin	204,252	189,009	180,861
Operating expenses:
Selling expenses	57,219	54,720	55,172
Research and development expenses	11,592	9,305	7,325
General and administrative expenses	27,690	27,729	27,526
Total operating expenses	96,501	91,754	90,023
Earnings from operations	107,751	97,255	90,838
Other expenses:
Interest expense, net	7,611	7,532	7,256
Other, net	1,110	1,235	648
Earnings before income tax expense	99,030	88,488	82,934
Income tax expense/(benefit)	20,457	(1,583)	26,962
Net earnings	$ 78,573	$ 90,071	$ 55,972
Basic net earnings per common share (in dollars per share)	$ 2.45	$ 2.83	$ 1.78
Diluted net earnings per common share (in dollars per share)	$ 2.42	$ 2.79	$ 1.75