Condensed Consolidated Statements of Earnings - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Net sales	$ 161,554	$ 163,687	$ 318,583	$ 325,097
Cost of sales	107,636	110,221	215,570	220,172
Gross margin	53,918	53,466	103,013	104,925
Operating expenses:
Selling expenses	15,494	14,495	29,620	28,554
Research and development expenses	2,852	3,230	5,747	5,799
General and administrative expenses	9,170	8,638	14,764	16,229
Total operating expenses	27,516	26,363	50,131	50,582
Earnings from operations	26,402	27,103	52,882	54,343
Other expenses:
Interest expense, net	1,488	2,265	3,077	4,139
Other, net	33	(223)	131	(34)
Total other expenses (income)	1,521	2,042	3,208	4,105
Earnings before income tax expense	24,881	25,061	49,674	50,238
Income tax expense	5,052	5,382	11,062	11,213
Net earnings	$ 19,829	$ 19,679	$ 38,612	$ 39,025
Net earnings per common share - basic (in dollars per share)	$ 0.62	$ 0.61	$ 1.20	$ 1.22
Net earnings per common share - diluted (in dollars per share)	$ 0.61	$ 0.61	$ 1.19	$ 1.21