Condensed Consolidated Statements of Earnings - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Net sales	$ 158,595	$ 155,043	$ 477,178	$ 480,140
Cost of sales	104,587	107,041	320,157	327,213
Gross margin	54,008	48,002	157,021	152,927
Operating expenses:
Selling expenses	15,227	14,229	44,847	42,783
Research and development expenses	2,699	2,540	8,446	8,339
General and administrative expenses	10,052	5,710	24,816	21,939
Total operating expenses	27,978	22,479	78,109	73,061
Earnings from operations	26,030	25,523	78,912	79,866
Other expenses:
Interest expense, net	1,672	1,797	4,749	5,936
Other, net	(78)	197	53	163
Total other expenses (income)	1,594	1,994	4,802	6,099
Earnings before income tax expense	24,436	23,529	74,110	73,767
Income tax expense	3,760	4,315	14,822	15,528
Net earnings	$ 20,676	$ 19,214	$ 59,288	$ 58,239
Net earnings per common share - basic (in dollars per share)	$ 0.64	$ 0.60	$ 1.84	$ 1.82
Net earnings per common share - diluted (in dollars per share)	$ 0.64	$ 0.59	$ 1.82	$ 1.79