Other Intangible Assets Net - Amortization Expense for Identified Intangible Assets (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Oct. 26, 2012	Oct. 28, 2011	Oct. 26, 2012	Oct. 28, 2011
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 21.5	$ 21.7	$ 42.9	$ 46.0
Developed Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	14.0	14.0	27.9	27.9
Customer Contracts/Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	6.3	6.4	12.6	15.4
Trademarks And Trade Names
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	1.0	1.1	2.0	2.3
Covenants Not To Compete
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 0.2	$ 0.2	$ 0.4	$ 0.4