Note 8 - Federal, State and Local Income Taxes (Details Textual)	6 Months Ended	12 Months Ended
Oct. 31, 2021	Oct. 31, 2020	Apr. 30, 2021	Apr. 30, 2020
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%	21.00%	21.00%
Effective Income Tax Rate Reconciliation, Percent, Total	19.05%	24.94%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent	1.11%	4.22%
Open Tax Year	2018 2019 2020
State and Local Jurisdiction [Member] \| New York City Department of Finance [Member]
Income Tax Examination, Year under Examination	2017 2018 2019

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Topic 740
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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 6.I.Fact.4)
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Tax year being audited in the income tax examination, in YYYY format.

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Tax year that remains open to examination under enacted tax laws, in YYYY format.

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