CONDENSED CONSOLIDATED STATEMENTS OF INCOME AND COMPREHENSIVE INCOME (unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
CONDENSED CONSOLIDATED STATEMENTS OF INCOME AND COMPREHENSIVE INCOME [Abstract]
Sales	$ 329,719	$ 289,923	$ 927,758	$ 804,104
Cost of sales	232,598	206,414	650,015	572,492
Gross profit	97,121	83,509	277,743	231,612
Selling, general and administrative expense	70,223	58,995	204,876	166,346
Operating income	26,898	24,514	72,867	65,266
Other income, net	(38)	(21)	(16)	(33)
Interest expense	1,614	2,287	4,930	3,878
Income before income taxes	25,322	22,248	67,953	61,421
Provision for income taxes	8,970	9,156	24,620	24,506
Net income	16,352	13,092	43,333	36,915
Preferred stock dividend	23	23	68	68
Net income attributable to common shareholders	16,329	13,069	43,265	36,847
Net income	16,352	13,092	43,333	36,915
Loss on long-term investment, net of income taxes	(13)	(5)	(755)	(286)
Cumulative translation adjustment	2,198	1,480	500	1,363
Comprehensive income	$ 18,537	$ 14,567	$ 43,078	$ 37,992
Basic earnings per share (in dollars per share)	$ 1.13	$ 0.91	$ 3.00	$ 2.56
Weighted average common shares outstanding (in shares)	14,444	14,411	14,430	14,375
Diluted earnings per share (in dollars per share)	$ 1.07	$ 0.86	$ 2.84	$ 2.43
Weighted average common shares and common equivalent shares outstanding (in shares)	15,284	15,251	15,270	15,215