Note 7 - Federal, State and Local Income Taxes - Effective Income Tax Rate Reconciliation (Details) (Parentheticals)	12 Months Ended
Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016
U.S. statutory federal tax rate		30.33%	35.00%	35.00%
Scenario, Forecast [Member]
U.S. statutory federal tax rate	21.00%

Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-SubTopic 10
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