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Goodwill And Intangible Assets (Narrative) (Detail) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Apr. 30, 2012
Apr. 30, 2011
Apr. 30, 2010
Goodwill And Intangible Assets [Abstract]      
Amortization expense $ 2.2 $ 2.4 $ 1.7