Warrants (Details) (USD $)	3 Months Ended			9 Months Ended
	Jan. 25, 2013	Oct. 26, 2012	Jan. 27, 2012	Jan. 25, 2013 item	Jan. 27, 2012	Dec. 07, 2012	Apr. 27, 2012	Sep. 27, 2005 Convertible Subordinated Debt [Member]
Warrants [Line Items]
Senior Notes								$ 125,000,000
Proceeds from warrants sold, September 2005				25,200,000
Number of common stock a warrant entitles holder to purchase	3,012,050			3,012,050
Exercise price of warrant (in Dollars per Unit)	50.00			50.00
Total settlement measurement period (in Duration)				60 days
Net-cash settlement equal to the market price excess over the strike price (in Dollars per Unit)				50.00
Approximate share basis for each tranche (in Shares)				50,000
Total number of tranches split into three groups for settlement (in Tranches)				60
Number of tranches per settlement group (in Tranches)				20
Cash settlement election for the first two groups (in Tranches)				40
Fair market value of first 40 tranches reclassed from common stock warrants to warrant liability				3,649,637
Remaining warrant equity of first 40 tranches reclassed to additional paid-in capital				13,200,000
Historic fair market value of first 40 tranches reclassed from common stock warrants to additional paid-in capital							25,200,000
Warrants' liability revalued		2,321,951
Shares issued - warrant conversion						27,919
Gain on warrants' liability	$ (2,112)	$ 2,321,951	$ 0	$ 1,325,574	$ 0