Condensed Consolidated Statements of Earnings (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Condensed Consolidated Statements of Earnings (unaudited) [Abstract]
Net sales	$ 150,716	$ 138,509	$ 435,526	$ 412,444
Cost of sales	104,535	93,853	298,155	278,515
Gross margin	46,181	44,656	137,371	133,929
Operating expenses:
Selling expenses	13,656	13,601	40,937	41,182
Research and development expenses	2,712	1,681	6,807	5,543
General and administrative expenses	6,758	6,428	19,038	20,957
Total operating expenses	23,126	21,710	66,782	67,682
Earnings from operations	23,055	22,946	70,589	66,247
Other expenses (income):
Interest income	(2)	(2)	(5)	(7)
Interest expense	2,012	1,790	5,702	5,538
Other, net	348	387	926	581
Earnings before income tax expense	20,697	20,771	63,966	60,135
Income tax expense	4,654	6,759	15,870	20,087
Net earnings	$ 16,043	$ 14,012	$ 48,096	$ 40,048
Net earnings per common share - basic (in dollars per share)	$ 0.50	$ 0.44	$ 1.51	$ 1.27
Net earnings per common share - diluted (in dollars per share)	$ 0.50	$ 0.44	$ 1.49	$ 1.26