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Earnings Per Share - Additional Information (Detail) (Stock Options [Member])
3 Months Ended 9 Months Ended
Jan. 31, 2014
Jan. 31, 2013
Jan. 31, 2014
Jan. 31, 2013
Stock Options [Member]
       
Earnings Per Share [Line Items]        
Antidilutive options exclude from computation of earning per share 36,600 118,400 36,600 118,400