Condensed Consolidated Statements Of Income (USD $)	3 Months Ended		9 Months Ended
	Jan. 25, 2013	Jan. 27, 2012	Jan. 25, 2013	Jan. 27, 2012
Condensed Consolidated Statements Of Income [Abstract]
Net sales	$ 62,700,033	$ 54,536,585	$ 185,976,849	$ 160,893,723
Cost of sales	5,367,218	4,099,489	15,548,199	15,182,188
Gross profit	57,332,815	50,437,096	170,428,650	145,711,535
Operating expenses:
Selling, general and administrative	26,646,935	24,941,131	82,539,731	76,529,794
Research and development	10,244,322	9,097,722	30,006,041	26,206,572
Total operating expenses	36,891,257	34,038,853	112,545,772	102,736,366
Income from operations	20,441,558	16,398,243	57,882,878	42,975,169
Interest income	21,129	84,124	40,634	244,443
Interest expense	(12,271)	(69,478)	(101,043)	(250,297)
Impairment of investment	0	0	(4,058,768)	0
Gain on warrants' liability	(2,112)	0	1,325,574	0
Other expense, net	(116,375)	(269,800)	(174,270)	(481,730)
Income before income taxes	20,331,929	16,143,089	54,915,005	42,487,585
Income tax expense	7,148,435	6,640,905	20,089,574	17,073,073
Net income	$ 13,183,494	$ 9,502,184	$ 34,825,431	$ 25,414,512
Basic income per share (in Dollars per Share)	$ 0.48	$ 0.34	$ 1.26	$ 0.91
Diluted income per share (in Dollars per Share)	$ 0.47	$ 0.34	$ 1.24	$ 0.90
Shares used in computing basic income per share (in Shares)	27,736,639	27,559,729	27,626,387	27,912,114
Shares used in computing diluted income per share (in Shares)	28,124,433	28,034,515	28,045,437	28,374,784