Business Combinations - Preliminary Fair Values of Assets Acquired and Liabilities Assumed (Detail) (USD $) In Millions, unless otherwise specified	Jan. 23, 2015	Apr. 25, 2014
Business Acquisition [Line Items]
Goodwill	$ 1,031.3us-gaap_Goodwill	$ 988.1us-gaap_Goodwill
Fiscal 2015 Acquisitions
Business Acquisition [Line Items]
Prepaid expenses and other current assets	2.7
Finite-lived intangible assets	31.8
Goodwill	43.2
Deferred income taxes	6.9
Other non-current assets	1.1
Total assets acquired	85.7
Deferred revenues	(1.1)
Total purchase price	$ 84.6

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Amount of assets acquired at the acquisition date.

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Amount of asset related to consideration paid in advance for costs that provide economic benefits in future periods, and amount of other assets that are expected to be realized or consumed within one year or the normal operating cycle, if longer, acquired at the acquisition date.

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Amount of deferred revenue expected to be recognized as such within one year or the normal operating cycle, if longer, assumed at the acquisition date.

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Amount of deferred tax asset attributable to deductible temporary differences and carryforwards that are expected to be realized or consumed after one year or the normal operating cycle, if longer, acquired at the acquisition date.

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The amount of identifiable intangible assets recognized as of the acquisition date.

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Amount of other assets expected to be realized or consumed after one year or the normal operating cycle, if longer, acquired at the acquisition date.

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Amount recognized for assets, including goodwill, in excess of (less than) the aggregate liabilities assumed.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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