Quarterly Results of Operations (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Apr. 30, 2013	Jan. 26, 2013	Oct. 27, 2012	Jul. 28, 2012	Apr. 30, 2012	Jan. 28, 2012	Oct. 29, 2011	Jul. 30, 2011	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011
Quarterly Results of Operations (Unaudited)
Revenue	$ 54,110	$ 47,087	$ 80,278	$ 58,677	$ 110,675	$ 71,964	$ 80,372	$ 61,997	$ 240,152	$ 325,008	$ 292,503
Gross margin	17,722	19,673	35,636	19,505	49,555	27,433	30,630	21,715	92,536	129,333	117,151
Net income	$ (795)	$ 3,869	$ 8,738	$ (1,386)	$ 17,794	$ 5,744	$ 6,587	$ 326	$ 10,426	$ 30,451	$ 25,909
Net (loss) income per share-basic (in dollars per share)	$ (0.04)	$ 0.17	$ 0.40	$ (0.06)	$ 0.81	$ 0.26	$ 0.30	$ 0.02	$ 0.47	$ 1.40	$ 1.20
Net (loss) income per share-diluted (in dollars per share)	$ (0.04)	$ 0.17	$ 0.39	$ (0.06)	$ 0.80	$ 0.26	$ 0.30	$ 0.01	$ 0.47	$ 1.36	$ 1.17