Financing Arrangements - Carrying Value of Long-Term Debt (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	9 Months Ended	12 Months Ended
Jun. 10, 2008	Jan. 25, 2013	Apr. 27, 2012
Debt Instrument [Line Items]
Long-term debt face amount		$ 2,264.9	$ 1,264.9
Less: Unamortized discount		(27.3)	(62.6)
Total		2,237.6	1,202.3
Less: Current portion		(1,243.3)	(1,202.3)
Total long-term debt		994.3	0
Senior Notes due 2017
Debt Instrument [Line Items]
Long-term debt face amount		750.0	0
Debt Instrument, Interest Rate, Effective Percentage		2.25%
Senior Notes Due 2022
Debt Instrument [Line Items]
Long-term debt face amount		250.0	0
Debt Instrument, Interest Rate, Effective Percentage		3.43%
Convertible Notes Payable
Debt Instrument [Line Items]
Long-term debt face amount	1,265.0	1,264.9	1,264.9
Less: Unamortized discount	$ (248.0)
Debt Instrument, Interest Rate, Effective Percentage	6.31%	6.31%	6.31%

The effective interest rate on the liability component of convertible debt instrument which may be settled in cash upon conversion, including partial cash settlement.

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The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount.

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Carrying amount of long-term debt, net of unamortized discount or premium, scheduled to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Carrying amount of long-term debt, net of unamortized discount or premium, excluding amounts to be repaid within one year or the normal operating cycle, if longer (current maturities). Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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