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Share-Based Payments (Details Textual) (USD $)
In Thousands, except Share data, unless otherwise specified
12 Months Ended
Apr. 30, 2011
Apr. 30, 2010
Apr. 30, 2009
Share-Based Payments (Textuals) [Abstract]      
Shares available for future issuance 7,600,347    
Weighted-average remaining contractual term for stock options outstanding and exercisable, in years 2.6    
Aggregate intrinsic value of stock options $ 6,673    
Intrinsic value of options exercised 13,355 5,876 2,871
Fair value of equity awards other than stock options vesting $ 17,680 $ 16,273 $ 11,117
Restricted stock, vesting period (in Years) 4 years