Deferred Compensation And Retirement Plans (Expected Benefit Payments Associated With Future Service) (Detail) (USD $) In Thousands, unless otherwise specified	Apr. 30, 2012
Deferred Compensation Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
2013	$ 5,601
2014	6,134
2015	6,067
2016	6,075
2017	5,997
2018-2022	28,276
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
2013	275
2014	308
2015	314
2016	310
2017	317
2018-2022	$ 1,334

The amount of the aggregate benefits expected to be paid in the five fiscal years thereafter (the aggregate amount of benefits expected to be paid in years 6 through 10 after the date of the latest statement of financial position).

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph f

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=6962843&loc=d3e1928-114920

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