Condensed Consolidated Statements of Earnings (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Condensed Consolidated Statements of Earnings (unaudited) [Abstract]
Net sales	$ 137,728	$ 135,141
Cost of sales	93,299	92,317
Gross margin	44,429	42,824
Operating expenses:
Selling expenses	13,712	13,087
Research and development expenses	1,815	1,942
General and administrative expenses	6,199	7,827
Total operating expenses	21,726	22,856
Earnings from operations	22,703	19,968
Other expenses (income):
Interest income	(2)	(3)
Interest expense	1,799	1,843
Other, net	196	147
Earnings before income tax expense	20,710	17,981
Income tax expense	5,192	6,095
Net earnings	$ 15,518	$ 11,886
Net earnings per common share - basic (in dollars per share)	$ 0.49	$ 0.38
Net earnings per common share - diluted (in dollars per share)	$ 0.48	$ 0.37