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Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Oct. 31, 2011	Oct. 31, 2010	Oct. 31, 2011	Oct. 31, 2010
Income Taxes (Textual) [Abstract]
Effective tax rate	34.10%	32.50%	33.70%	32.00%
Amount unrecognized tax benefit could decrease in next 12 months	$ 1.1		$ 1.1

- Definition

A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

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