Annual report pursuant to Section 13 and 15(d)

Property And Equipment (Parenthetical) (Detail)

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Property And Equipment (Parenthetical) (Detail) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Apr. 30, 2013
Apr. 30, 2012
Apr. 30, 2011
Property, Plant and Equipment [Line Items]      
Depreciation expense for capitalized software $ 4.0 $ 2.5 $ 2.3