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Earnings Per Share - Additional Information (Detail) (Stock Options [Member])
3 Months Ended 6 Months Ended
Oct. 31, 2014
Oct. 31, 2013
Oct. 31, 2014
Oct. 31, 2013
Stock Options [Member]
       
Earnings Per Share [Line Items]        
Anti-dilutive options excluded from computation of earnings per share 70,800 48,050 70,800 48,050