QUARTERLY FINANCIAL INFORMATION (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 166,527	$ 158,595	$ 161,554	$ 157,029	$ 163,539	$ 155,043	$ 163,687	$ 161,410	$ 643,705	$ 643,679	$ 594,790
Gross profit	54,346	54,008	53,918	49,095	51,325	48,002	53,466	51,459	211,367	204,252	189,009
Earnings before income taxes	22,368	24,436	24,881	24,793	25,263	23,529	25,061	25,177	96,478	99,030	88,488
Net earnings	$ 20,383	$ 20,676	$ 19,829	$ 18,783	$ 20,334	$ 19,214	$ 19,679	$ 19,346	$ 79,671	$ 78,573	$ 90,071
Basic net earnings per common share (in dollars per share)	$ 0.64	$ 0.64	$ 0.62	$ 0.58	$ 0.63	$ 0.60	$ 0.61	$ 0.60	$ 2.48	$ 2.45	$ 2.83
Diluted net earnings per common share (in dollars per share)	$ 0.63	$ 0.64	$ 0.61	$ 0.58	$ 0.63	$ 0.59	$ 0.61	$ 0.60	$ 2.45	$ 2.42	$ 2.79