Summary of Significant Accounting Policies - Concentrations of Portfolio Company Values Compared to the Fair Value of the Corporation's Total Investment Portfolio (Details)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Tilson
Accounting Policies [Line Items]
Concentration risk investment portfolio	16.00%	14.00%
FSS
Accounting Policies [Line Items]
Concentration risk investment portfolio	10.00%	10.00%
Seybert's
Accounting Policies [Line Items]
Concentration risk investment portfolio	11.00%	8.00%
Sciaps
Accounting Policies [Line Items]
Concentration risk investment portfolio		7.00%
INEA
Accounting Policies [Line Items]
Concentration risk investment portfolio		6.00%
Mattison
Accounting Policies [Line Items]
Concentration risk investment portfolio	8.00%
Caitec
Accounting Policies [Line Items]
Concentration risk investment portfolio	6.00%