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Note 1 - Organization and Summary of Significant Accounting Policies - Schedule of Fair Value Measurements of Investments (Details) - USD ($) | Jan. 31, 2022 | Apr. 30, 2021
--- | --- | ---
Equity Securities, FV-NI, Total | $ 27,316,000 | $ 23,582,000
Available-for-sale fixed income securities | 597,000 | 2,600,000
Investments, Fair Value Disclosure, Total | 56,994,000 | 44,391,000
Money Market Funds [Member] |  |
Cash and cash equivalents | (29,081,000) | (18,209,000)
Cash and cash equivalents | 29,081,000 | 18,209,000
Fair Value, Inputs, Level 1 [Member] |  |
Equity Securities, FV-NI, Total | 27,316,000 | 23,582,000
Available-for-sale fixed income securities | 597,000 | 2,600,000
Investments, Fair Value Disclosure, Total | 56,994,000 | 44,391,000
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member] |  |
Cash and cash equivalents | (29,081,000) | (18,209,000)
Cash and cash equivalents | 29,081,000 | 18,209,000
Fair Value, Inputs, Level 2 [Member] |  |
Equity Securities, FV-NI, Total | 0 | 0
Available-for-sale fixed income securities | 0 | 0
Investments, Fair Value Disclosure, Total | 0 | 0
Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member] |  |
Cash and cash equivalents | 0 | 0
Cash and cash equivalents | 0 | 0
Fair Value, Inputs, Level 3 [Member] |  |
Equity Securities, FV-NI, Total | 0 | 0
Available-for-sale fixed income securities | 0 | 0
Investments, Fair Value Disclosure, Total | 0 | 0
Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member] |  |
Cash and cash equivalents | 0 | 0
Cash and cash equivalents | $ 0 | $ 0

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- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(6)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=124260329&loc=d3e26610-111562 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27161-111563 + Details
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- Definition Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References No definition available. + Details
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- Definition Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=123594786&loc=SL75136599-209740 + Details
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