Consolidated Statements Of Income (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
Net sales	$ 556,247	$ 561,294	$ 542,569	$ 498,763	$ 553,162	$ 575,646	$ 512,561	$ 461,926	$ 2,158,873	$ 2,103,295	$ 1,974,198
Cost of sales	484,546	489,088	470,998	432,152	484,427	505,210	445,667	403,107	1,876,784	1,838,411	1,744,298
Gross profit	71,701	72,206	71,571	66,611	68,735	70,436	66,894	58,819	282,089	264,884	229,900
Selling, general and administrative expenses	57,063	55,906	56,903	56,450	56,952	54,554	54,477	51,290	226,322	217,273	191,233
Special charges				1,135					1,135
Income from operations	14,638	16,300	14,668	9,026	11,783	15,882	12,417	7,529	54,632	47,611	38,667
Interest expense	(33)	(69)	(64)		(148)	(93)	(87)	(41)	(166)	(369)	(490)
Other, net	18	6	(29)	46	60	32	32	65	41	189	213
Income before taxes	14,623	16,237	14,575	9,072	11,695	15,821	12,362	7,553	54,507	47,431	38,390
Income tax provision	(5,754)	(6,336)	(5,749)	(3,597)	(4,268)	(6,435)	(4,882)	(3,059)	(21,436)	(18,644)	(15,429)
Net income	$ 8,869	$ 9,901	$ 8,826	$ 5,475	$ 7,427	$ 9,386	$ 7,480	$ 4,494	$ 33,071	$ 28,787	$ 22,961
Earnings per common share:
Basic	$ 0.34	$ 0.37	$ 0.33	$ 0.21	$ 0.28	$ 0.35	$ 0.28	$ 0.17	$ 1.25	$ 1.08	$ 0.85
Diluted	$ 0.33	$ 0.37	$ 0.33	$ 0.21	$ 0.28	$ 0.35	$ 0.28	$ 0.17	$ 1.24	$ 1.07	$ 0.85
Shares used in computation of earnings per common share:
Basic	26,413	26,470	26,403	26,439	26,451	26,615	26,852	26,901	26,431	26,703	27,007
Diluted	26,598	26,660	26,519	26,586	26,599	26,692	26,923	26,986	26,586	26,800	27,053