Quarterly Financial Data (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Apr. 30, 2014	Jan. 31, 2014	Oct. 31, 2013	Jul. 31, 2013	Apr. 30, 2013	Jan. 31, 2013	Oct. 31, 2012	Jul. 31, 2012	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012
Quarterly Financial Data [Abstract]
Net sales	$ 188,855	$ 169,033	$ 190,532	$ 178,095	$ 171,079	$ 151,346	$ 159,760	$ 148,252	$ 726,515	$ 630,437	$ 515,814
Gross profit	32,187	26,001	32,274	33,715	32,312	23,507	24,794	22,043	124,177	102,656	66,475
Income before income taxes	9,404	4,953	8,631	10,682	8,878	3,476	3,371	1,015	33,670	16,740	(33,288)
Net income (loss)	$ 5,634	$ 2,901	$ 5,271	$ 6,655	$ 5,190	$ 2,057	$ 1,950	$ 561	$ 20,461	$ 9,758	$ (20,786)
Basic	$ 0.36	$ 0.19	$ 0.35	$ 0.45	$ 0.36	$ 0.14	$ 0.13	$ 0.04	$ 1.34	$ 0.67	$ (1.45)
Diluted	$ 0.36	$ 0.18	$ 0.34	$ 0.43	$ 0.35	$ 0.14	$ 0.13	$ 0.04	$ 1.31	$ 0.66	$ (1.45)