Note 6 - Comprehensive Income - Components of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020
Change in unrealized gains (losses) on securities, amount before tax			$ 2,407	$ 592
Change in unrealized gains (losses) on securities, tax expense			(626)	(260)
Change in unrealized gains (losses) on securities, amount net of tax			1,781	332
Less: Gains realized in net income			(1,162)
Less: Gains realized in net income, tax			302
Less: Gains realized in net income, net of tax			(860)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax, Portion Attributable to Parent, Total			1,245	592
Other Comprehensive Income (Loss), Available-for-sale Securities, Tax, Portion Attributable to Parent, Total			(324)	(260)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent, Total	$ 947	$ (30)	$ 921	$ 332

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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