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Note 6 - Fair Value - Significant Level 3 Fair Value Measurement Inputs (Details) - Fair Value, Inputs, Level 3 [Member] $ in Thousands | Jun. 30, 2023 USD ($) | Dec. 31, 2022 USD ($)
--- | --- | ---
Investments, fair value |  | $ 713,244 |  | $ 716,319 |
Investments, measurement input |  | 100 |  |  |
Debt [Member] | Valuation Technique, Discounted Cash Flow [Member] |  |  |  |  |
Investments, fair value |  | $ 611,524 |  | $ 669,617 |
Debt [Member] | Valuation Technique, Discounted Cash Flow [Member] | Minimum [Member] | Hypothetical Market Yield [Member] |  |  |  |  |
Investments, measurement input |  | 0.11 |  | 0.03 |
Debt [Member] | Valuation Technique, Discounted Cash Flow [Member] | Maximum [Member] | Hypothetical Market Yield [Member] |  |  |  |  |
Investments, measurement input |  | 0.24 | [1] | 0.22 |
Debt [Member] | Valuation Technique, Discounted Cash Flow [Member] | Weighted Average [Member] | Hypothetical Market Yield [Member] |  |  |  |  |
Investments, measurement input |  | 0.14 |  | 0.14 | [1]
Debt [Member] | Multiple Probability Weighted Cash Flow Model [Member] |  |  |  |  |
Investments, fair value |  | $ 71,785 |  | $ 16,545 |
Debt [Member] | Multiple Probability Weighted Cash Flow Model [Member] | Minimum [Member] | Probability Weighting [Member] |  |  |  |  |
Investments, measurement input |  | 0.05 |  | 0.10 |
Debt [Member] | Multiple Probability Weighted Cash Flow Model [Member] | Maximum [Member] | Probability Weighting [Member] |  |  |  |  |
Investments, measurement input |  | 1 | [1] | 0.75 |
Debt [Member] | Multiple Probability Weighted Cash Flow Model [Member] | Weighted Average [Member] | Probability Weighting [Member] |  |  |  |  |
Investments, measurement input |  | 0.50 |  | 0.31 | [1]
Debt [Member] | Black-scholes Valuation Model [Member] |  |  |  |  |
Investments, fair value |  |  |  | $ 26,145 |
Debt [Member] | Black-scholes Valuation Model [Member] | Measurement Input, Price Volatility [Member] |  |  |  |  |
Investments, measurement input |  |  |  | 0.28 |
Debt [Member] | Black-scholes Valuation Model [Member] | Measurement Input, Discount for Lack of Marketability [Member] |  |  |  |  |
Investments, measurement input |  |  |  | 20 |
Debt [Member] | Black-scholes Valuation Model [Member] | Minimum [Member] | Measurement Input, Share Price [Member] |  |  |  |  |
Investments, measurement input |  |  |  | 0.00 |
Debt [Member] | Black-scholes Valuation Model [Member] | Minimum [Member] | Estimated Time to Exit [Member] |  |  |  |  |
Investments, measurement input |  |  |  | 1 |
Debt [Member] | Black-scholes Valuation Model [Member] | Maximum [Member] | Measurement Input, Share Price [Member] |  |  |  |  |
Investments, measurement input |  |  |  | 1.899 |
Debt [Member] | Black-scholes Valuation Model [Member] | Maximum [Member] | Estimated Time to Exit [Member] |  |  |  |  |
Investments, measurement input |  |  |  | 5 |
Debt [Member] | Black-scholes Valuation Model [Member] | Weighted Average [Member] | Measurement Input, Share Price [Member] |  |  |  |  |
Investments, measurement input | [1] |  |  | 58.52 |
Debt [Member] | Black-scholes Valuation Model [Member] | Weighted Average [Member] | Measurement Input, Price Volatility [Member] |  |  |  |  |
Investments, measurement input | [1] |  |  | 0.28 |
Debt [Member] | Black-scholes Valuation Model [Member] | Weighted Average [Member] | Measurement Input, Discount for Lack of Marketability [Member] |  |  |  |  |
Investments, measurement input | [1] |  |  | 20 |
Debt [Member] | Black-scholes Valuation Model [Member] | Weighted Average [Member] | Estimated Time to Exit [Member] |  |  |  |  |
Investments, measurement input | [1] |  |  | 3 |
Debt [Member] | Convertible Note Analysis [Member] |  |  |  |  |
Investments, fair value |  |  |  | $ 296 |
Debt [Member] | Convertible Note Analysis [Member] | Measurement Input, Share Price [Member] |  |  |  |  |
Investments, measurement input |  |  |  | 168.93 |
Debt [Member] | Convertible Note Analysis [Member] | Weighted Average [Member] | Measurement Input, Share Price [Member] |  |  |  |  |
Investments, measurement input | [1] |  |  | 168.93 |
Warrant [Member] | Black-scholes Valuation Model [Member] |  |  |  |  |
Investments, fair value |  | $ 24,314 |  |  |
Warrant [Member] | Black-scholes Valuation Model [Member] | Measurement Input, Price Volatility [Member] |  |  |  |  |
Investments, measurement input |  | 0.28 |  |  |
Warrant [Member] | Black-scholes Valuation Model [Member] | Measurement Input, Discount for Lack of Marketability [Member] |  |  |  |  |
Investments, measurement input |  | 0.20 |  |  |
Warrant [Member] | Black-scholes Valuation Model [Member] | Minimum [Member] | Measurement Input, Share Price [Member] |  |  |  |  |
Investments, measurement input |  | 0.00 |  |  |
Warrant [Member] | Black-scholes Valuation Model [Member] | Minimum [Member] | Measurement Input, Discount for Lack of Marketability [Member] |  |  |  |  |
Investments, measurement input |  | 0.20 |  |  |
Warrant [Member] | Black-scholes Valuation Model [Member] | Minimum [Member] | Estimated Time to Exit [Member] |  |  |  |  |
Investments, measurement input |  | 1 |  |  |
Warrant [Member] | Black-scholes Valuation Model [Member] | Maximum [Member] | Measurement Input, Share Price [Member] |  |  |  |  |
Investments, measurement input | [1] | 1,899 |  |  |
Warrant [Member] | Black-scholes Valuation Model [Member] | Maximum [Member] | Estimated Time to Exit [Member] |  |  |  |  |
Investments, measurement input | [1] | 5 |  |  |
Warrant [Member] | Black-scholes Valuation Model [Member] | Weighted Average [Member] | Measurement Input, Share Price [Member] |  |  |  |  |
Investments, measurement input |  | 59.21 |  |  |
Warrant [Member] | Black-scholes Valuation Model [Member] | Weighted Average [Member] | Measurement Input, Price Volatility [Member] |  |  |  |  |
Investments, measurement input |  | 0.28 |  |  |
Warrant [Member] | Black-scholes Valuation Model [Member] | Weighted Average [Member] | Estimated Time to Exit [Member] |  |  |  |  |
Investments, measurement input |  | 3 |  |  |
Warrant [Member] | Expected Proceeds [Member] |  |  |  |  |
Investments, fair value |  | $ 62 |  |  |
Warrant [Member] | Expected Proceeds [Member] | Measurement Input, Share Price [Member] |  |  |  |  |
Investments, measurement input |  | 0.25 |  |  |
Warrant [Member] | Expected Proceeds [Member] | Weighted Average [Member] | Measurement Input, Share Price [Member] |  |  |  |  |
Investments, measurement input |  | 0.25 |  |  |
Other Investments [Member] | Multiple Probability Weighted Cash Flow Model [Member] |  |  |  |  |
Investments, fair value |  | $ 1,300 |  | $ 1,300 |
Other Investments [Member] | Multiple Probability Weighted Cash Flow Model [Member] | Probability Weighting [Member] |  |  |  |  |
Investments, measurement input |  |  |  | 100 |
Other Investments [Member] | Multiple Probability Weighted Cash Flow Model [Member] | Measurement Input, Discount Rate [Member] |  |  |  |  |
Investments, measurement input |  | 0.25 |  | 0.25 |
Other Investments [Member] | Multiple Probability Weighted Cash Flow Model [Member] | Weighted Average [Member] | Probability Weighting [Member] |  |  |  |  |
Investments, measurement input | [1] |  |  | 100 |
Other Investments [Member] | Multiple Probability Weighted Cash Flow Model [Member] | Weighted Average [Member] | Measurement Input, Discount Rate [Member] |  |  |  |  |
Investments, measurement input |  | 0.25 |  | 0.25 | [1]
Equity Securities [Member] | Last Equity Financing [Member] |  |  |  |  |
Investments, fair value |  | $ 4,259 |  | $ 2,416 |
Equity Securities [Member] | Last Equity Financing [Member] | Weighted Average [Member] | Measurement Input, Share Price [Member] |  |  |  |  |
Investments, measurement input |  | 27.56 |  | 26.93 | [1]
[1] | Weighted average is calculated by multiplying (a) the unobservable input for each investment in the investment type by (b) (1) the fair value of the related investment in the investment type divided by (2) the total fair value of the investment type.

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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 -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482106/820-10-50-2 + Details
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