Goodwill and Purchased Intangible Assets Net - Other Intangible Assets Net (Detail) (USD $) In Millions, unless otherwise specified	Apr. 26, 2013	Apr. 27, 2012
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Assets	$ 379.2	$ 358.4
Accumulated Amortization	(198.6)	(122.4)
Net Assets	180.6	236.0
Developed Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Assets	312.4	282.1
Accumulated Amortization	(134.9)	(79.0)
Net Assets	177.5	203.1
Customer Contracts/Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Assets	54.7	59.4
Accumulated Amortization	(53.1)	(32.7)
Net Assets	1.6	26.7
Trademarks And Trade Names
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Assets	9.9	14.7
Accumulated Amortization	(8.9)	(9.7)
Net Assets	1.0	5.0
Covenants Not To Compete
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Assets	2.2	2.2
Accumulated Amortization	(1.7)	(1.0)
Net Assets	$ 0.5	$ 1.2