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Stock Options and Share-Based Compensation - Summary of Stock Option Activity and Weighted Average Exercise Price (Detail) - $ / shares	12 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017
Number of Shares
Outstanding at beginning of year (in shares)	137,250	180,350
Canceled (in shares)	(13,100)	(6,300)
Exercised (in shares)	(19,800)	(36,800)
Outstanding at end of year (in shares)	104,350	137,250
Exercisable at end of year (in shares)	84,550	79,100
Weighted Average Exercise Price
Outstanding at beginning of year (in dollar per shares)	$ 18.28	$ 18.01	$ 17.29
Canceled (in dollar per shares)	21.03	19.09
Exercised (in dollar per shares)	14.54	14.31
Outstanding at end of year (in dollar per shares)	18.28	18.01	$ 17.29
Exercisable at end of year (in dollar per shares)	$ 17.63	$ 16.28

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- Definition

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Number of share options (or share units) exercised during the current period.

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