Stockholders Equity - Additional Information Related to Stock Options (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	9 Months Ended
Jan. 25, 2013	Jan. 27, 2012	Jan. 25, 2013	Jan. 27, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average fair value per share granted	$ 20.53	$ 13.26	$ 11.54	$ 16.88
Intrinsic value of options exercised	$ 15.0	$ 21.0	$ 30.8	$ 71.6
Proceeds received from the exercise of stock options	15.8	19.5	35.3	62.2
Fair value of options vested	$ 14.5	$ 18.1	$ 44.0	$ 56.8

The cash inflow associated with the amount received from holders exercising their stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately.

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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-Name Statement of Financial Accounting Standard (FAS)

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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-Name Statement of Financial Accounting Standard (FAS)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

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+ Details