Stock-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
Jul. 31, 2020	Jul. 31, 2019
Share-based Payment Arrangement [Abstract]
Option to purchase common stock (in shares)	535,000	47,000
Stock-based compensation expense	$ 546	$ 443
Income tax excess benefit	$ 234	$ 62
Stock options exercised (in shares)	230,747	151,500
Total intrinsic value of options exercised	$ 1,400	$ 600
Unrecognized compensation cost related to unvested stock option	$ 6,800
Weighted average period for unrecognized compensation cost	1 year 11 months 8 days

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of cost to be recognized for option under share-based payment arrangement.

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Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

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Amount of noncash expense for share-based payment arrangement.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Gross number of share options (or share units) granted during the period.

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

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