Financing Arrangements - Amount of Interest Expense Recognized Related to Convertible Notes (Detail) (Convertible Notes Payable, USD $) In Millions, unless otherwise specified	3 Months Ended
Jul. 26, 2013	Jul. 27, 2012
Convertible Notes Payable
Debt Instrument [Line Items]
Contractual coupon interest expense	$ 2.5	$ 5.5
Amortization of debt discount	7.1	13.5
Amortization of debt issuance costs	0.6	1.2
Less capitalized interest	0	(0.5)
Total interest expense related to Convertible Notes	$ 10.2	$ 19.7

Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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Amount of noncash expense included in interest expense to issue debt and obtain financing associated with the related debt instruments. Alternate captions include noncash interest expense.

+ References

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Interest expense related to convertible debt instruments which has been recognized for the period, including the contractual interest coupon and amortization of the debt discount, if any.

+ References

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-Publisher FASB

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Amount of interest capitalized, including amount of allowance for funds used during construction.

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-Publisher FASB

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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Represents the portion of interest incurred in the period on debt arrangements that was charged against earnings, excluding amortization of debt discount (premium) and financing costs.

+ References

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