Stockholders' Equity - Activity Related to Stock Options (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
Apr. 24, 2015	Apr. 25, 2014	Apr. 26, 2013
Number of Shares
Beginning balance, Number of Shares	14.5	19.2	20.6
Options granted, Number of Shares	2.2	2.9	2.4
Options exercised, Number of Shares	(4.6)	(6.3)	(3.0)
Options forfeited and expired, Number of Shares	(0.6)	(1.3)	(0.8)
Ending balance, Number of Shares	11.5	14.5	19.2
Options vested and expected to vest, Number of Shares	11.1
Options Exercisable, Number of Shares	7.9
Weighted-Average Exercise Price
Beginning balance, Weighted-Average Exercise Price	$ 34.10	$ 31.27	$ 29.98
Options granted, Weighted-Average Exercise Price	$ 36.64	$ 38.26	$ 28.87
Options exercised, Weighted-Average Exercise Price	$ 25.25	$ 25.83	$ 18.37
Options forfeited and expired, Weighted-Average Exercise Price	$ 42.42	$ 42.47	$ 40.11
Ending balance, Weighted-Average Exercise Price	$ 37.74	$ 34.10	$ 31.27
Options vested and expected to vest, Weighted-Average Exercise Price	$ 37.78
Options Exercisable, Weighted-Average Exercise Price	$ 38.32
Weighted-Average Remaining Contractual Term and Aggregate Intrinsic Value
Outstanding, Weighted-Average Remaining Contractual Term	3 years 8 months 12 days
Options vested and expected to vest, Weighted-Average Remaining Contractual Term	3 years 7 months 17 days
Exercisable, Weighted-Average Remaining Contractual Term	2 years 10 months 21 days
Outstanding, Aggregate Intrinsic Value	$ 29.8
Options vested and expected to vest, Aggregate Intrinsic Value	29.5
Exercisable, Aggregate Intrinsic Value	$ 26.1

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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Weighted average price of options that were either forfeited or expired.

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Gross number of share options (or share units) granted during the period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of fully vested and expected to vest options outstanding.

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As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

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As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected to vest.

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Weighted average remaining contractual term for fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Number of share options (or share units) exercised during the current period.

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