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, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
CONDENSED CONSOLIDATED STATEMENTS OF INCOME AND COMPREHENSIVE INCOME (unaudited) [Abstract]
Sales	$ 387,053	$ 329,719	$ 1,117,160	$ 927,758
Cost of sales	273,644	232,598	790,998	650,015
Gross profit	113,409	97,121	326,162	277,743
Selling, general and administrative expense	81,605	70,223	243,798	204,876
Operating income	31,804	26,898	82,364	72,867
Other expense (income), net	10	(38)	1	(16)
Interest expense	3,295	1,614	9,868	4,930
Income before income taxes	28,499	25,322	72,495	67,953
Provision for income taxes	10,856	8,970	27,695	24,620
Net income	17,643	16,352	44,800	43,333
Preferred stock dividend	23	23	68	68
Net income attributable to common shareholders	17,620	16,329	44,732	43,265
Net income	17,643	16,352	44,800	43,333
Loss on long-term investment, net of income taxes	0	(13)	(55)	(755)
Cumulative translation adjustment	(1,137)	2,198	(1,752)	500
Comprehensive income	$ 16,506	$ 18,537	$ 42,993	$ 43,078
Basic earnings per share (in dollars per share)	$ 1.20	$ 1.13	$ 3.04	$ 3.00
Weighted average common shares outstanding (in shares)	14,656	14,444	14,696	14,430
Diluted earnings per share (in dollars per share)	$ 1.14	$ 1.07	$ 2.88	$ 2.84
Weighted average common shares and common equivalent shares outstanding (in shares)	15,496	15,284	15,536	15,270