QUARTERLY FINANCIAL INFORMATION (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
QUARTERLY FINANCIAL INFORMATION (UNAUDITED) [Abstract]
Net sales	$ 140,760	$ 138,509	$ 138,794	$ 135,141	$ 132,729	$ 140,128	$ 134,773	$ 144,862	$ 553,204	$ 552,492	$ 541,383
Gross profit	46,932	44,656	46,449	42,824	39,926	43,174	41,867	43,130	180,861	168,097	144,172
Earnings before income taxes	22,799	20,771	21,383	17,981	20,623	21,189	22,167	23,085	82,934	87,063	77,052
Net earnings	$ 15,924	$ 14,012	$ 14,150	$ 11,886	$ 15,659	$ 13,976	$ 14,916	$ 15,172	$ 55,972	$ 59,722	$ 52,826
Basic net earnings per common share (in dollars per share)	$ 0.51	$ 0.44	$ 0.45	$ 0.38	$ 0.50	$ 0.45	$ 0.48	$ 0.49	$ 1.78	$ 1.92	$ 1.74
Diluted net earnings per common share (in dollars per share)	$ 0.50	$ 0.44	$ 0.44	$ 0.37	$ 0.49	$ 0.44	$ 0.47	$ 0.48	$ 1.75	$ 1.89	$ 1.69