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Note 6 - Fair Value Measurements (Details Textual) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019 | Nov. 13, 2014
Debt Securities, Available-for-sale, Unrealized Gain (Loss), Total | $ (200) | $ 0 | $ (100) | $ 0 |
Class of Warrant or Right, Outstanding (in shares) | 0 |  | 0 |  |
Hudson Warrant [Member] |  |  |  |  |
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares) |  | 818,181 |  | 818,181 | 58,823
Maximum [Member] | Certificates of Deposit [Member] |  |  |  |  |
Marketable Securities, Realized Gain (Loss), Total |  | $ 100 |  | $ 100 |

X
- Definition Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644 + Details
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X
- Definition Number of warrants or rights outstanding. + References No definition available. + Details
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X
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- Definition Amount of realized gain (loss) on investment in marketable security, including other-than-temporary impairment (OTTI). + References No definition available. + Details
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