Other Intangible Assets Net - Amortization Expense for Identified Intangible Assets (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jul. 27, 2012	Jul. 29, 2011
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 21.4	$ 24.3
Developed Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	13.9	13.9
Customer Contracts/Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	6.3	9.0
Trademarks And Trade Names
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	1.0	1.2
Covenants Not To Compete
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 0.2	$ 0.2