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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, 2024 USD ($)		Dec. 31, 2023 USD ($)
Investments, fair value		$ 646,232		$ 706,858
Multiple Probability Weighted Cash Flow Model [Member] | Minimum [Member] | Probability Weighting [Member]
Investments, measurement input		0
Multiple Probability Weighted Cash Flow Model [Member] | Maximum [Member] | Probability Weighting [Member]
Investments, measurement input		0.20
Debt [Member] | Valuation Technique, Discounted Cash Flow [Member]
Investments, fair value		$ 556,542		$ 617,529
Debt [Member] | Valuation Technique, Discounted Cash Flow [Member] | Minimum [Member] | Hypothetical Market Yield [Member]
Investments, measurement input		0.12		11
Debt [Member] | Valuation Technique, Discounted Cash Flow [Member] | Maximum [Member] | Hypothetical Market Yield [Member]
Investments, measurement input		0.25		24
Debt [Member] | Valuation Technique, Discounted Cash Flow [Member] | Weighted Average [Member] | Hypothetical Market Yield [Member]
Investments, measurement input	[1]	0.15		15
Debt [Member] | Multiple Probability Weighted Cash Flow Model [Member]
Investments, fair value		$ 52,526		$ 52,643
Debt [Member] | Multiple Probability Weighted Cash Flow Model [Member] | Minimum [Member] | Probability Weighting [Member]
Investments, measurement input		0.05		20
Debt [Member] | Multiple Probability Weighted Cash Flow Model [Member] | Maximum [Member] | Probability Weighting [Member]
Investments, measurement input		1		100
Debt [Member] | Multiple Probability Weighted Cash Flow Model [Member] | Weighted Average [Member] | Probability Weighting [Member]
Investments, measurement input	[1]	0.64		50
Warrant [Member] | Black-scholes Valuation Model [Member]
Investments, fair value		$ 21,069		$ 22,913
Warrant [Member] | Black-scholes Valuation Model [Member] | Measurement Input, Price Volatility [Member]
Investments, measurement input		0.25		25
Warrant [Member] | Black-scholes Valuation Model [Member] | Expected Proceeds [Member]
Investments, fair value				$ 62
Warrant [Member] | Black-scholes Valuation Model [Member] | Minimum [Member] | Measurement Input, Share Price [Member]
Investments, measurement input		0		0
Warrant [Member] | Black-scholes Valuation Model [Member] | Minimum [Member] | Measurement Input, Discount for Lack of Marketability [Member]
Investments, measurement input		0.17	[1]	0
Warrant [Member] | Black-scholes Valuation Model [Member] | Minimum [Member] | Estimated Time to Exit [Member]
Investments, measurement input		1		1
Warrant [Member] | Black-scholes Valuation Model [Member] | Maximum [Member] | Measurement Input, Share Price [Member]
Investments, measurement input		1,898.58		1,899
Warrant [Member] | Black-scholes Valuation Model [Member] | Maximum [Member] | Measurement Input, Discount for Lack of Marketability [Member]
Investments, measurement input				20
Warrant [Member] | Black-scholes Valuation Model [Member] | Maximum [Member] | Estimated Time to Exit [Member]
Investments, measurement input		5		5
Warrant [Member] | Black-scholes Valuation Model [Member] | Weighted Average [Member] | Measurement Input, Share Price [Member]
Investments, measurement input	[1]	74.78		64.95
Warrant [Member] | Black-scholes Valuation Model [Member] | Weighted Average [Member] | Measurement Input, Price Volatility [Member]
Investments, measurement input	[1]	0.25		25
Warrant [Member] | Black-scholes Valuation Model [Member] | Weighted Average [Member] | Measurement Input, Discount for Lack of Marketability [Member]
Investments, measurement input	[1]			18
Warrant [Member] | Black-scholes Valuation Model [Member] | Weighted Average [Member] | Estimated Time to Exit [Member]
Investments, measurement input	[1]	3		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		0.25
Warrant [Member] | Expected Proceeds [Member] | Weighted Average [Member] | Measurement Input, Share Price [Member]
Investments, measurement input	[1]	0.25		0.25
Other Investments [Member] | Multiple Probability Weighted Cash Flow Model [Member]
Investments, fair value		$ 9,183		$ 6,430
Other Investments [Member] | Multiple Probability Weighted Cash Flow Model [Member] | Measurement Input, Discount Rate [Member]
Investments, measurement input		0.25		25
Other Investments [Member] | Multiple Probability Weighted Cash Flow Model [Member] | Minimum [Member] | Probability Weighting [Member]
Investments, measurement input		0.30		30
Other Investments [Member] | Multiple Probability Weighted Cash Flow Model [Member] | Maximum [Member] | Probability Weighting [Member]
Investments, measurement input		1		100
Other Investments [Member] | Multiple Probability Weighted Cash Flow Model [Member] | Weighted Average [Member] | Probability Weighting [Member]
Investments, measurement input	[1]	0.75		81
Other Investments [Member] | Multiple Probability Weighted Cash Flow Model [Member] | Weighted Average [Member] | Measurement Input, Discount Rate [Member]
Investments, measurement input	[1]	0.25		25
Equity Securities [Member] | Last Equity Financing [Member]
Investments, fair value		$ 6,850		$ 7,281
Equity Securities [Member] | Last Equity Financing [Member] | Minimum [Member] | Measurement Input, Share Price [Member]
Investments, measurement input		0		0.56
Equity Securities [Member] | Last Equity Financing [Member] | Maximum [Member] | Measurement Input, Share Price [Member]
Investments, measurement input		215.03		215.03
Equity Securities [Member] | Last Equity Financing [Member] | Weighted Average [Member] | Measurement Input, Share Price [Member]
Investments, measurement input	[1]	22.31		17.15
[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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+ References

No definition available.

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- Definition

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+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2E
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2E

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-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

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