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Note 1 - Organization and Summary of Significant Accounting Policies - Schedule of Fair Value Measurements of Investments (Details) - USD ($) $ in Thousands | Jul. 31, 2020 | Apr. 30, 2020
--- | --- | ---
Securities available-for-sale | $ 30,673 | $ 29,204
Investments, Fair Value Disclosure, Total | 37,819 | 31,319
Money Market Funds [Member] |  |
Cash equivalents | 7,146 | 2,115
Fair Value, Inputs, Level 1 [Member] |  |
Securities available-for-sale | 30,673 | 29,204
Investments, Fair Value Disclosure, Total | 37,819 | 31,319
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member] |  |
Cash equivalents | 7,146 | 2,115
Fair Value, Inputs, Level 2 [Member] |  |
Securities available-for-sale |  |
Investments, Fair Value Disclosure, Total |  |
Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member] |  |
Cash equivalents |  |
Fair Value, Inputs, Level 3 [Member] |  |
Securities available-for-sale |  |
Investments, Fair Value Disclosure, Total |  |
Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member] |  |
Cash equivalents |  |

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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 Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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