Purchased Intangible Assets, Net - Amortization Expense for Purchased Intangible Assets (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jul. 25, 2014	Jul. 26, 2013
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 14.5	$ 14.9
Cost of revenues | Developed Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	14.3	14.3
Operating expenses | Customer Contracts/Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	0.1	0.4
Operating expenses | Trademarks And Trade Names
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	0.1	0.1
Operating expenses | Covenants not to Compete
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 0	$ 0.1