Investments (Schedule of Long-term Investments) (Details) (USD $)	3 Months Ended				9 Months Ended					9 Months Ended		3 Months Ended
	Jan. 25, 2013		Jul. 27, 2012	Jan. 27, 2012	Jan. 25, 2013		Jan. 27, 2012	Apr. 27, 2012		Jan. 25, 2013 Neuro Vista Corporation [Member]	Oct. 26, 2011 Im Thera Medical Inc [Member]	Oct. 26, 2012 Cerbomed GmbH [Member]
Investment [Line Items]
Available-for-sale convertible debt security	$ 1,450,000	[1]			$ 1,450,000	[1]		$ 5,508,768	[1]
Cost method equity securities	6,588,200	[2]			6,588,200	[2]		4,000,000	[2]		4,000,000
Carrying amount - long-term investments	8,038,200				8,038,200			9,508,768
Interest rate of securities (in Percent)					6.00%
Impairment of investment in NeuroVista	0		4,508,768	0	4,058,768		0
Investment in convertible preferred stock					$ 2,588,200		$ 4,000,000					$ 2,588,200
Debt Instrument, Maturity Date										May 01, 2013

[1] The available-for-sale convertible debt security was issued by NeuroVista Corporation (“NeuroVista”). NeuroVista is a privately-held company focused on the development of an implantable device that is intended to inform patients when seizures are likely to occur, as well as to alert caregivers when seizures do occur. Under its terms, this debt matures in May 2013, unless earlier converted to stock. The interest rate on this debt is 6%, which is payable at maturity or convertible to stock. Cumulative interest was included in the carrying value of the investment as of April 27, 2012. During the quarter ended July 27, 2012, we recorded an other-than-temporary impairment loss of $4,508,768 based on our determination that the fair value of the investment was below the carrying value. Refer to “Note 17. Fair Value Measurements” for further details regarding this security, its fair value assessment and the impairment loss recorded.

[2] In October 2011, we invested $4.0 million in the convertible preferred stock of ImThera Medical, Inc. (“ImThera”). ImThera is a privately-held company focused on the development of a neurostimulation device system for the treatment of obstructive sleep apnea. In September 2012, we invested $2,588,200 in the preferred stock of Cerbomed GmbH (“Cerbomed”). Cerbomed is a privately-held German company focused on developing a transcutaneous vagus nerve stimulation device for the treatment of epilepsy. Neither of these investments provided us significant influence over the entity involved. See “Note 17. Fair Value Measurements” for further details.