Condensed Consolidated Statements of Earnings (unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Condensed Consolidated Statements of Earnings (unaudited) [Abstract]
Net sales	$ 138,794	$ 134,773	$ 273,935	$ 279,635
Cost of sales	92,345	92,906	184,662	194,638
Gross margin	46,449	41,867	89,273	84,997
Operating expenses:
Selling expenses	14,494	11,367	27,581	23,153
Research and development expenses	1,920	1,492	3,862	2,940
General and administrative expenses	6,702	5,234	14,529	10,092
Total operating expenses	23,116	18,093	45,972	36,185
Earnings from operations	23,333	23,774	43,301	48,812
Other expenses (income):
Interest income	(2)	(3)	(5)	(5)
Interest expense	1,905	1,594	3,748	3,475
Other, net	47	16	194	90
Earnings before income tax expense	21,383	22,167	39,364	45,252
Income tax expense	7,233	7,251	13,328	15,164
Net earnings	$ 14,150	$ 14,916	$ 26,036	$ 30,088
Net earnings per common share - basic (in dollars per share)	$ 0.45	$ 0.48	$ 0.83	$ 0.97
Net earnings per common share - diluted (in dollars per share)	$ 0.44	$ 0.47	$ 0.82	$ 0.95