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Employee Stock Plans (Weighted Average Assumptions Used To Estimate Fair Value Of Each Employee Stock Option And SARs) (Details)
3 Months Ended
Jul. 31, 2011
years
Jul. 31, 2010
years
Employee Stock Plans    
Expected volatility 47.07% 47.67%
Risk-free interest rate 1.47% 1.83%
Expected option life (in years) 5.00 5.00
Expected dividend yield 0.00% 0.00%