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Note 4 - Investments - Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Investments at cost	$ 766,774	$ 759,182
Investments at fair value	697,891	709,085
Biotechnology Sector [Member]
Investments at cost	118,221	145,544
Investments at fair value	97,562	117,781
Medical Device Sector [Member]
Investments at cost	213,564	147,064
Investments at fair value	205,634	145,019
Communications Sector [Member]
Investments at cost	11,711	19,192
Investments at fair value	14,763	22,188
Consumer-related Sector [Member]
Investments at cost	74,421	105,669
Investments at fair value	36,667	101,327
Data Storage Sector [Member]
Investments at cost	417	417
Investments at fair value	350	418
Internet and Media Sector [Member]
Investments at cost	329	329
Investments at fair value	999	1,582
Networking Sector [Member]
Investments at cost	10,070	5,451
Investments at fair value	9,827	5,297
Power Management Sector [Member]
Investments at cost	0	1,585
Investments at fair value	0	2,700
Semiconductor Sector [Member]
Investments at cost	45	45
Investments at fair value	0	0
Software Sector [Member]
Investments at cost	154,040	164,133
Investments at fair value	151,043	160,749
Energy Efficiency [Member]
Investments at cost	9,818	111
Investments at fair value	9,712	13
Other Sustainability Sector [Member]
Investments at cost	66,151	98,906
Investments at fair value	66,079	80,370
Diagnostics Sector [Member]
Investments at cost	16,704	19,735
Investments at fair value	13,701	19,701
Other Healthcare Sector [Member]
Investments at cost	39,533	102
Investments at fair value	40,144	1,366
Software, Healthcare Information and Service [Member]
Investments at cost	51,750	50,899
Investments at fair value	51,410	50,574
Debt [Member]
Investments at cost	678,167	721,231
Investments at fair value	638,779	670,172
Warrant [Member]
Investments at cost	15,956	16,526
Investments at fair value	18,277	24,594
Other Debt Obligations [Member]
Investments at cost	36,709	6,982
Investments at fair value	14,637	6,430
Equity Securities [Member]
Investments at cost	35,942	14,443
Investments at fair value	$ 26,198	$ 7,889

X

- Definition

Cost of the investment.

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