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Employee Benefit Plans - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Apr. 30, 2014
Apr. 30, 2013
Apr. 30, 2012
Employee Stock Purchase Plan [Line Items]      
Employer contributions $ 784 $ 645 $ 603
Defined contribution plan , description We provide an employer matching contribution equal to fifty cents for every dollar an employee invests in the 401(k) Plan up to our maximum match of one thousand dollars per calendar year, subject to revision.    
Employer contributions vesting period Three year    
Class A Common Stock [Member]
      
Employee Stock Purchase Plan [Line Items]      
Discount rate 15.00%    
Reserve for stock issuance 900    
Stock issued under stock purchase plan 70 76 65
Stock available for distribution under stock purchase plan 113