Unaudited Quarterly Financial Data (Detail) (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
Quarterly Financial Information [Line Items]
Net sales	$ 47,150	$ 61,360	$ 67,866	$ 74,614	$ 62,168	$ 67,299	$ 63,318	$ 59,811	$ 250,990	$ 252,596	$ 189,423
Gross profit margin	5,967	9,337	11,570	14,275	11,904	12,574	12,172	10,798
Operating income	1,752	4,652	7,307	9,692	7,013	7,231	8,475	6,968	23,403	29,687	20,423
Provision for income taxes	54	1,333	2,222	2,725	2,212	2,774	2,975	2,395	6,334	10,356	6,821
Net income	$ 1,081	$ 2,745	$ 4,505	$ 6,286	$ 4,256	$ 3,893	$ 5,525	$ 4,448	$ 14,617	$ 18,122	$ 13,242
Basic	$ 0.16	$ 0.40	$ 0.66	$ 0.92	$ 0.62	$ 0.57	$ 0.81	$ 0.65	$ 2.13	$ 2.65	$ 1.95
Diluted	$ 0.16	$ 0.38	$ 0.62	$ 0.86	$ 0.59	$ 0.55	$ 0.79	$ 0.64	$ 2.02	$ 2.56	$ 1.93