Net Income per Share - Computation of Basic and Diluted Net Income Per Share (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	9 Months Ended
Jan. 23, 2015	Jan. 24, 2014	Jan. 23, 2015	Jan. 24, 2014
Net income per share:
Net income	$ 176.8us-gaap_NetIncomeLoss	$ 192.1us-gaap_NetIncomeLoss	$ 425.0us-gaap_NetIncomeLoss	$ 440.5us-gaap_NetIncomeLoss
Shares used in basic computation	311.6	339.4	317.8	343.7
Dilutive impact of employee equity award plans	5.5	6.8	5.5	7.0
Dilutive impact of assumed conversion of Convertible Notes	0	0	0	0.7
Dilutive impact of warrants	0	0	0	0.3
Shares used in diluted computation	317.1	346.2	323.3	351.7
Basic	$ 0.57us-gaap_EarningsPerShareBasic	$ 0.57us-gaap_EarningsPerShareBasic	$ 1.34us-gaap_EarningsPerShareBasic	$ 1.28us-gaap_EarningsPerShareBasic
Diluted	$ 0.56us-gaap_EarningsPerShareDiluted	$ 0.55us-gaap_EarningsPerShareDiluted	$ 1.31us-gaap_EarningsPerShareDiluted	$ 1.25us-gaap_EarningsPerShareDiluted

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of call options and warrants using the treasury stock method.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of convertible debt securities using the if-converted method.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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