Derivatives and Hedging Activities - Schedule of Notional Value of Outstanding Foreign Currency Forward Contracts (Detail) (United States of America, Dollars, USD $) In Millions, unless otherwise specified	Oct. 25, 2013	Apr. 26, 2013
Cash Flow Hedging | Long
Derivative [Line Items]
Forward contracts, Notional Amount	$ 181.3	$ 108.4
Balance Sheet Contracts | Long
Derivative [Line Items]
Forward contracts, Notional Amount	258.7	358.4
Balance Sheet Contracts | Short
Derivative [Line Items]
Forward contracts, Notional Amount	$ 180.3	$ 158.2