Statements of Consolidated Shareholders' Equity (Parenthetical) (USD $)	12 Months Ended
Apr. 30, 2011	Apr. 30, 2010	Apr. 30, 2009
Statement of Consolidated Shareholders' Equity [Abstract]
Dividend declared per common share	$ 1.68	$ 1.45	$ 6.31

Aggregate dividends declared during the period for each share of common stock outstanding.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Article 3

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Namespace Prefix:	us-gaap
Data Type:	us-types:perShareItemType
Balance Type:	na
Period Type:	duration