Note 6 - Comprehensive Income - Components of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Change in unrealized gains (losses) on securities, amount before tax			$ 890	$ 457
Change in unrealized gains (losses) on securities, tax expense			(232)	(95)
Change in unrealized gains (losses) on securities, amount net of tax			658	362
Less: Gains realized in net income			(925)
Less: Gains realized in net income, tax			241
Less: Gains realized in net income, net of tax			(684)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax, Portion Attributable to Parent, Total			(35)	457
Other Comprehensive Income (Loss), Available-for-sale Securities, Tax, Portion Attributable to Parent, Total			9	(95)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent, Total	$ (146)	$ 276	$ (26)	$ 362

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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