Note 12 - Beneficial Ownership (Details Textual)	12 Months Ended
Dec. 31, 2025
Star Equity Fund L.P. [Member]
Investment Company, Beneficial Ownership, Percentage of Voting Securities Held	29.45%

The percentage of voting securities held under beneficial ownership.

No definition available.

Name:	svvc_InvestmentCompanyBeneficialOwnershipPercentageOfVotingSecuritiesHeld
Namespace Prefix:	svvc_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration