QUARTERLY FINANCIAL INFORMATION (UNAUDITED) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
QUARTERLY FINANCIAL INFORMATION (UNAUDITED) [Abstract]
Net sales	$ 80,060	$ 75,116	$ 79,014	$ 76,203	$ 69,733	$ 74,439	$ 74,687	$ 73,008	$ 310,393	$ 291,867	$ 255,071
Gross profit	22,399	23,398	22,584	21,158	20,843	22,617	21,761	20,780	89,539	86,001	78,037
Earnings before income taxes	15,107	16,225	14,824	13,688	13,772	15,238	14,352	13,376	59,844	56,738	50,131
Net earnings	$ 9,892	$ 10,873	$ 9,972	$ 9,268	$ 9,496	$ 10,785	$ 9,572	$ 8,912	$ 40,005	$ 38,765	$ 33,277
Basic net earnings per common share (in dollars per share)	$ 0.34	$ 0.37	$ 0.34	$ 0.32	$ 0.33	$ 0.38	$ 0.34	$ 0.31	$ 1.38	$ 1.36	$ 1.19
Diluted net earnings per common share (in dollars per share)	$ 0.33	$ 0.36	$ 0.33	$ 0.31	$ 0.31	$ 0.36	$ 0.32	$ 0.30	$ 1.32	$ 1.28	$ 1.12