Note 6 - Comprehensive Income - Components of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Oct. 31, 2022	Oct. 31, 2021	Oct. 31, 2022	Oct. 31, 2021
Change in unrealized losses on available-for-sale fixed income securities, before tax			$ 3	$ (5)
Change in unrealized losses on available-for-sale fixed income securities, tax			(1)	1
Change in unrealized losses on available-for-sale fixed income securities, after tax			2	(4)
Other Comprehensive Income (Loss), Available-for-Sale Securities Adjustment, before Tax, Portion Attributable to Parent, Total			3	(5)
Other comprehensive income (loss), available-for-sale securities, tax expense			(1)	1
Other comprehensive income (loss), available-for-sale securities adjustment, amount net of tax	$ (3)	$ 0	$ 2	$ (4)

Amount before tax, after reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities, attributable to parent entity. Excludes amounts related to other than temporary impairment (OTTI) loss.

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