Goodwill and Purchased Intangible Assets Net - Other Intangible Assets Net (Detail) (USD $) In Millions, unless otherwise specified	Jan. 25, 2013	Apr. 27, 2012
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Assets	$ 370.9	$ 358.4
Accumulated Amortization	(177.1)	(122.4)
Net Assets	193.8	236.0
Developed Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Assets	304.1	282.1
Accumulated Amortization	(120.8)	(79.0)
Net Assets	183.3	203.1
Customer Contracts/Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Assets	54.7	59.4
Accumulated Amortization	(46.8)	(32.7)
Net Assets	7.9	26.7
Trademarks And Trade Names
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Assets	9.9	14.7
Accumulated Amortization	(8.0)	(9.7)
Net Assets	1.9	5.0
Covenants Not To Compete
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Assets	2.2	2.2
Accumulated Amortization	(1.5)	(1.0)
Net Assets	$ 0.7	$ 1.2