Purchased Intangible Assets, Net - Amortization Expense for Purchased Intangible Assets (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Jan. 24, 2014	Jan. 25, 2013	Jan. 24, 2014	Jan. 25, 2013
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 14.7	$ 21.4	$ 44.5	$ 64.3
Cost of revenues | Developed Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	14.2	13.9	42.8	41.8
Operating expenses | Customer Contracts/Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	0.3	6.3	1.0	18.9
Operating expenses | Trademarks And Trade Names
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	0.1	1.1	0.3	3.1
Operating expenses | Covenants Not To Compete
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 0.1	$ 0.1	$ 0.4	$ 0.5