Financing Arrangements - Carrying Value of Convertible Debt (Detail) (USD $) In Millions, unless otherwise specified	Oct. 26, 2012	Apr. 27, 2012	Jun. 10, 2008
Debt Instrument [Line Items]
Less: Unamortized discount			$ (248.0)
Net carrying amount of Notes	1,229.4	1,202.3
Convertible Senior Notes 1.75%
Debt Instrument [Line Items]
1.75% Convertible Senior Notes due 2013	1,264.9	1,264.9	1,265.0
Less: Unamortized discount	(35.5)	(62.6)
Net carrying amount of Notes	$ 1,229.4	$ 1,202.3

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 21

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

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-Section 55

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Name:	us-gaap_DebtInstrumentUnamortizedDiscount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant