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Employee Incentive Plans Defined Contribution Plans (Details) (Defined Contribution Pension [Member], USD $)
12 Months Ended
Apr. 30, 2012
Apr. 30, 2011
Defined Contribution Pension [Member]
   
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]    
401(k) Contributions by Employer $ 10,000 $ 5,000