Summary of Activities Related to Dividends on Common Stock (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
Jul. 25, 2014	Jul. 26, 2013
Dividends, Common Stock [Abstract]
Dividends per share declared and paid	$ 0.165	$ 0.150
Dividend payments allocated to retained earnings	$ 53.4	$ 51.4
Retained Earnings
Dividends, Common Stock [Abstract]
Dividend payments allocated to retained earnings	$ 53.4	$ 51.4

Cash outflow in the form of capital distributions and dividends to common shareholders, preferred shareholders and noncontrolling interests.

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration