Stockholders Equity - Income Tax Effects Associated with Employee Stock Transactions (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
Jan. 24, 2014	Jan. 25, 2013
Tax Benefit (Deficiency) Associated with Share Based Compensation Plan [Line Items]
Income tax benefits associated with employee stock transactions	$ 22.5	$ 35.4

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