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Income Taxes (Narrative) (Detail) (USD $)
12 Months Ended
Apr. 30, 2011
Apr. 30, 2010
Apr. 30, 2012
Income Taxes [Abstract]      
Temporary difference resulting from earnings from non-US subsidiaries which are permanently reinvested outside the United States     $ 113,600,000
Federal statute of limitations expired $ 2,131,000 $ 10,329,000