QUARTERLY FINANCIAL DATA (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
Selected Quarterly Financial Information [Abstract]
Net sales	$ 71,917		$ 70,636		$ 69,327		$ 66,749		$ 65,026	$ 64,767	$ 63,348	$ 60,899	$ 278,629		$ 254,040	$ 223,356
Gross profit	16,239		18,584		16,967		16,518		14,515	15,332	15,245	14,558	68,308		59,650	51,500
Net income	951	[1]	5,639	[1]	5,105	[1]	4,792	[1]	4,076	4,078	3,966	4,269	16,487	[1]	16,389	12,931
Amounts per common share [Abstract]
Net income (in dollars per share)	$ 0.08		$ 0.48		$ 0.44		$ 0.41		$ 0.35	$ 0.35	$ 0.34	$ 0.37	$ 1.41		$ 1.42	$ 1.13
Net income - assuming dilution (in dollars per share)	$ 0.08		$ 0.48		$ 0.43		$ 0.41		$ 0.35	$ 0.35	$ 0.34	$ 0.37	$ 1.39		$ 1.40	$ 1.11
Acquisition fees	$ 4,860												$ 5,362		$ 0	$ 0

[1] The fourth quarter of 2012 includes $4,860 in acquisition fees related to Valent.