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v3.20.2

Note 8 - Employees' Profit Sharing and Savings Plan (Details Textual) - USD ($) | 12 Months Ended
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Apr. 30, 2020 | Apr. 30, 2019 | Apr. 30, 2018
Deferred Compensation Arrangement with Individual, Contributions by Employer | $ 870,000 | $ 592,000 | $ 496,000

X
- Definition Amount of contributions made by employer into fund established for purposes of making future disbursement to individual in accordance with deferred compensation arrangement. + References No definition available. + Details
Name: | us-gaap_DeferredCompensationArrangementWithIndividualContributionsByEmployer
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration