XML 58 R47.htm IDEA: XBRL DOCUMENT v3.7.0.1
Stock Options and Share-Based Compensation - Summary of Stock Option Activity and Weighted Average Exercise Price (Detail) - $ / shares
 12 Months Ended
Apr. 30, 2017
Apr. 30, 2016
Apr. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]      
Number of Shares, Outstanding at beginning of year 185,375 239,575 228,250
Number of Shares, Granted 45,200 40,200 45,800
Number of Shares, Canceled (150) (10,400) (5,400)
Number of Shares, Exercised (50,075) (84,000) (29,075)
Number of Shares, Outstanding at end of year 180,350 185,375 239,575
Number of Shares, Exercisable at end of year 78,650 92,075 136,700
Weighted Average Exercise Price, Outstanding at beginning of year $ 14.68 $ 13.24 $ 12.17
Weighted Average Exercise Price, Granted 22.92 16.92 17.78
Weighted Average Exercise Price, Canceled 10.64 16.37 11.74
Weighted Average Exercise Price, Exercised 12.72 11.44 12.28
Weighted Average Exercise Price, Outstanding at end of year 17.29 14.68 13.24
Weighted Average Exercise Price, Exercisable at end of year $ 14.22 $ 12.83 $ 11.66