Consolidated Statements of Operations (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Net sales	$ 60,057	$ 46,419	$ 58,310	$ 39,318	$ 52,092	$ 36,319	$ 46,651	$ 34,410	$ 204,104	$ 169,472	$ 141,481
Cost of sales	39,037	28,228	36,932	24,278	32,027	23,267	28,786	20,486	128,475	104,566	85,877
Gross profit	21,020	18,191	21,378	15,040	20,065	13,052	17,865	13,924	75,629	64,906	55,604
Selling, general and administrative expenses		13,421	12,575	11,364	13,024	10,687	11,539	10,211	49,509	45,461	37,790
Income from operations		4,770	8,803	3,676	7,041	2,365	6,326	3,713	26,120	19,445	17,814
Interest expense		(80)	(104)	(71)	(48)	(40)	(40)	(40)	(335)	(168)	(161)
Other income (expense), net		30	32	26	(29)	31	36	49	41	87	(1,076)
Income before provision for income taxes	8,744	4,720	8,731	3,631	6,964	2,356	6,322	3,722	25,826	19,364	16,577
Provision for income taxes		1,951	3,511	1,459	3,099	934	2,558	1,521	10,537	8,112	6,541
Net income	5,128	2,769	5,220	2,172	3,865	1,422	3,764	2,201	15,289	11,252	10,036
Net income attributable to common stockholders									$ 15,289	$ 11,252	$ 303
Earnings per share
-Basic (in dollars per share)	$ 0.30	$ 0.16	$ 0.31	$ 0.13	$ 0.22	$ 0.08	$ 0.22	$ 0.13	$ 0.90	$ 0.66	$ 0.65
-Diluted (in dollars per share)	$ 0.29	$ 0.16	$ 0.30	$ 0.13	$ 0.22	$ 0.08	$ 0.21	$ 0.12	$ 0.88	$ 0.64	$ 0.27
Weighted average shares of common stock outstanding used in computing earnings per share
-Basic (shares)	17,005,472	16,937,139	16,896,227	16,869,557	17,262,253	17,249,536	17,070,327	16,936,007	16,926,827	17,129,334	469,089
-Diluted (shares)	17,425,573	17,398,006	17,392,447	17,353,222	17,724,131	17,781,720	17,702,516	17,600,908	17,412,548	17,707,839	1,111,088