This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13433-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13476-108611

Name:	us-gaap_DebtInstrumentFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Financial Instruments and Fair Value Measurements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Dec. 12, 2012 Senior Notes due 2017	Dec. 12, 2012 Senior Notes Due 2022	Apr. 26, 2013 Significant Other Observable Inputs (Level 2) Senior Notes	Apr. 26, 2013 Significant Other Observable Inputs (Level 2) Convertible Notes Payable	Apr. 27, 2012 Significant Other Observable Inputs (Level 2) Convertible Notes Payable	Apr. 26, 2013 Significant Other Observable Inputs (Level 2) Senior Notes due 2017	Apr. 26, 2013 Significant Other Observable Inputs (Level 2) Senior Notes Due 2022
Fair Value of Financial Instruments [Line Items]
Long-term Debt			$ 1,007.7	$ 1,393.6	$ 1,649.9
Notes issued, interest rate	2.00%	3.25%				2.00%	3.25%