Income Taxes - Effective Income Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
Apr. 30, 2022	Apr. 30, 2021	Apr. 30, 2020
Income Tax Disclosure [Abstract]
Computed “expected” income tax expense	$ 2,905	$ 1,858	$ 1,428
Increase (decrease) in income taxes resulting from:
State income taxes, net of federal income tax effect	396	323	214
Research and development credits	(522)	(640)	(703)
Excess tax benefits from stock option deductions	(1,737)	(641)	(737)
Foreign tax credits	(44)	(1)	(164)
Other, net, including permanent items	57	(140)	18
Income tax expense	$ 1,055	$ 759	$ 56

Amount of difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operation, attributable to expense for award under share-based payment arrangement. Excludes expense determined to be nondeductible upon grant or after for award under share-based payment arrangement.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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