QUARTERLY FINANCIAL INFORMATION (UNAUDITED) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
QUARTERLY FINANCIAL INFORMATION (UNAUDITED) [Abstract]
Net sales	$ 69,733	$ 74,439	$ 74,687	$ 73,008	$ 69,800	$ 63,910	$ 61,458	$ 59,903	$ 291,867	$ 255,071	$ 219,438
Gross profit	20,843	22,617	21,761	20,780	21,274	20,233	19,116	17,414	86,001	78,037	66,958
Earnings before income taxes	13,772	15,238	14,352	13,376	13,974	12,945	12,551	10,661	56,738	50,131	40,602
Net earnings	$ 9,496	$ 10,785	$ 9,572	$ 8,912	$ 9,416	$ 8,493	$ 8,339	$ 7,029	$ 38,765	$ 33,277	$ 26,785
Basic net earnings per common share (in dollars per share)	$ 0.33	$ 0.38	$ 0.34	$ 0.31	$ 0.33	$ 0.30	$ 0.30	$ 0.25	$ 1.36	$ 1.19	$ 0.98
Diluted net earnings per common share (in dollars per share)	$ 0.31	$ 0.36	$ 0.32	$ 0.30	$ 0.31	$ 0.29	$ 0.28	$ 0.24	$ 1.28	$ 1.12	$ 0.93