Purchased Intangible Assets, Net (Detail) (USD $) In Millions, unless otherwise specified	Jul. 26, 2013	Apr. 26, 2013
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Assets	$ 297.1	$ 379.2
Accumulated Amortization	(131.4)	(198.6)
Net Assets	165.7	180.6
Developed Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Assets	283.0	312.4
Accumulated Amortization	(119.8)	(134.9)
Net Assets	163.2	177.5
Customer Contracts/Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Assets	9.6	54.7
Accumulated Amortization	(8.4)	(53.1)
Net Assets	1.2	1.6
Trademarks And Trade Names
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Assets	2.9	9.9
Accumulated Amortization	(2.0)	(8.9)
Net Assets	0.9	1.0
Covenants Not To Compete
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Assets	1.6	2.2
Accumulated Amortization	(1.2)	(1.7)
Net Assets	$ 0.4	$ 0.5