Accounting Policies (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	12 Months Ended
Apr. 30, 2011	Apr. 30, 2010	Apr. 30, 2009
Basic and Diluted Earnings Per Share
Basic and diluted net income	$ 572	$ 449	$ 435
Income allocated to participating securities (restricted shares)	(1)	(1)	(1)
Net income available to common stockholders	$ 571	$ 448	$ 434
Share data
Basic average common shares outstanding	145,603	147,834	150,452
Dilutive effect of stock options, SSARs and RSUs	910	741	927
Diluted average common shares outstanding	146,513	148,575	151,379
Basic earnings per share	$ 3.92	$ 3.03	$ 2.88
Diluted earnings per share	$ 3.90	$ 3.02	$ 2.87

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Net Income or Loss Available to Common Stockholders plus adjustments resulting from the assumption that dilutive convertible securities were converted, options or warrants were exercised, or that other shares were issued upon the satisfaction of certain conditions.

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