Goodwill and Purchased Intangible Assets Net - Purchased Intangible Assets, Net (Detail) (USD $) In Millions, unless otherwise specified	Apr. 25, 2014	Apr. 26, 2013
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Assets	$ 297.1	$ 379.2
Accumulated Amortization	(175.6)	(198.6)
Net Assets	121.5	180.6
Developed Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Assets	283.0	312.4
Accumulated Amortization	(162.6)	(134.9)
Net Assets	120.4	177.5
Customer Contracts/Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Assets	9.6	54.7
Accumulated Amortization	(9.0)	(53.1)
Net Assets	0.6	1.6
Trademarks And Trade Names
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Assets	2.9	9.9
Accumulated Amortization	(2.4)	(8.9)
Net Assets	0.5	1.0
Covenants not to Compete
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Assets	1.6	2.2
Accumulated Amortization	(1.6)	(1.7)
Net Assets	$ 0	$ 0.5