Note 10 - Disclosure of Credit Risk of Financial Instruments with Off-balance Sheet Risk (Details Textual)	12 Months Ended
Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019
Customer Concentration Risk [Member] \| Revenue Benchmark [Member] \| One Single Customer [Member]
Concentration Risk, Percentage	31.60%	31.40%	20.50%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-Section 50
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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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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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