Stockholders Equity - Income Tax Effects Associated with Employee Stock Transactions (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
Oct. 25, 2013	Oct. 26, 2012
Tax Benefit (Deficiency) Associated with Share Based Compensation Plan [Line Items]
Income tax benefit associated with employee stock transactions	$ 1.8	$ 28.2

Amount of increase (decrease) in additional paid in capital (APIC) resulting from a tax benefit (deficiency) associated with an share-based compensation plan other than an employee stock ownership plan (ESOP).

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration