Debt (Details Textual) (USD $) In Millions, unless otherwise specified	Apr. 30, 2012
Debt (Textual) [Abstract]
2013	$ 3
2014	253
2016	$ 250
5.2% notes, due in fiscal 2012 [Member]
Debt Instrument [Line Items]
Interest rate on long term debt	5.20%
5.0% notes due in fiscal 2014 [Member]
Debt Instrument [Line Items]
Interest rate on long term debt	5.00%
2.5% notes, due in fiscal 2016 [Member]
Debt Instrument [Line Items]
Interest rate on long term debt	2.50%

Amount of long-term debt maturing within the next twelve months following the date of the latest balance sheet presented in the financial statements, which may include maturities of long-term debt, sinking fund requirements, and other securities redeemable at fixed or determinable prices and dates.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 47

-Paragraph 10

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 470

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

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