Income Taxes - Deferred Tax Assets and Liabilities (Detail) (USD $) In Millions, unless otherwise specified	Apr. 24, 2015	Apr. 25, 2014
Components of Deferred Tax Assets and Liabilities [Abstract]
Reserves and accruals	$ 94.3	$ 89.3
Acquired intangibles	43.8	22.3
Net operating loss and credit carryforwards	79.6	87.6
Stock-based compensation	70.4	73.3
Deferred revenue	297.7us-gaap_DeferredTaxAssetsDeferredIncome	318.9us-gaap_DeferredTaxAssetsDeferredIncome
Other	27.0us-gaap_DeferredTaxAssetsOther	19.8us-gaap_DeferredTaxAssetsOther
Gross deferred tax assets	612.8us-gaap_DeferredTaxAssetsGross	611.2us-gaap_DeferredTaxAssetsGross
Valuation allowance	(57.7)	(49.6)
Deferred tax assets, net of valuation allowance	555.1us-gaap_DeferredTaxAssetsNet	561.6us-gaap_DeferredTaxAssetsNet
Reserves and accruals	4.0	3.9
Acquired intangibles	13.7	10.0
Property and equipment	26.3	30.8
Other	3.5us-gaap_DeferredTaxLiabilitiesOther	2.6us-gaap_DeferredTaxLiabilitiesOther
Total deferred tax liabilities	47.5us-gaap_DeferredTaxLiabilities	47.3us-gaap_DeferredTaxLiabilities
Deferred tax assets, net of valuation allowance and deferred tax liabilities	$ 507.6us-gaap_DeferredTaxAssetsLiabilitiesNet	$ 514.3us-gaap_DeferredTaxAssetsLiabilitiesNet

Deferred tax assets in relation to the company's operating loss and credit carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from deferred income.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from intangible assets including goodwill.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

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Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, before jurisdictional netting.

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Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences not separately disclosed.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from share-based compensation.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from other reserves not separately disclosed.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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Amount, after deferred tax asset, of deferred tax liability attributable to taxable differences, before jurisdictional netting.

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Amount of deferred tax liability attributable to taxable temporary differences from reserves and accruals.

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Amount of deferred tax liability attributable to taxable temporary differences from intangible assets other than goodwill.

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Amount of deferred tax liability attributable to taxable temporary differences not separately disclosed.

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Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment.

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