Condensed Consolidated Statements of Earnings (unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Condensed Consolidated Statements of Earnings (unaudited) [Abstract]
Net sales	$ 147,082	$ 138,794	$ 284,810	$ 273,935
Cost of sales	100,321	92,345	193,620	184,662
Gross margin	46,761	46,449	91,190	89,273
Operating expenses:
Selling expenses	13,569	14,494	27,281	27,581
Research and development expenses	2,280	1,920	4,095	3,862
General and administrative expenses	6,081	6,702	12,280	14,529
Total operating expenses	21,930	23,116	43,656	45,972
Earnings from operations	24,831	23,333	47,534	43,301
Other expenses (income):
Interest income	(2)	(2)	(3)	(5)
Interest expense	1,891	1,905	3,690	3,748
Other, net	382	47	578	194
Earnings before income tax expense	22,560	21,383	43,269	39,364
Income tax expense	6,024	7,233	11,216	13,328
Net earnings	$ 16,536	$ 14,150	$ 32,053	$ 26,036
Net earnings per common share - basic (in dollars per share)	$ 0.52	$ 0.45	$ 1.01	$ 0.83
Net earnings per common share - diluted (in dollars per share)	$ 0.51	$ 0.44	$ 1.00	$ 0.82