Income Taxes - Effective Income Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2024	Apr. 30, 2023	Apr. 30, 2022
Income Tax Disclosure [Abstract]
Computed “expected” income tax expense	$ 2,433	$ 2,566	$ 2,570
Increase (decrease) in income taxes resulting from:
State income taxes, net of federal income tax effect	747	503	231
Change in valuation allowance	334	181	111
Research and development credits	(880)	(586)	(522)
Dividends received deduction	(209)	(123)	(37)
Excess tax benefits from stock option deductions	0	(70)	(1,727)
Foreign tax credits	(183)	(37)	(44)
Other, net, including permanent items	(353)	(196)	(20)
Income tax expense	$ 1,889	$ 2,238	$ 562