Summary of Significant Accounting Policies - Concentrations of Portfolio Company Values Compared to the Fair Value of the Corporation's Total Investment Portfolio (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2025	Dec. 31, 2024
Tilson
Accounting Policies [Line Items]
Concentration risk investment portfolio	19.00%	16.00%
Seybert's
Accounting Policies [Line Items]
Concentration risk investment portfolio	13.00%	11.00%
FSS
Accounting Policies [Line Items]
Concentration risk investment portfolio	11.00%	10.00%
EFINEA
Accounting Policies [Line Items]
Concentration risk investment portfolio	8.00%
Mattison
Accounting Policies [Line Items]
Concentration risk investment portfolio		8.00%
Caitec
Accounting Policies [Line Items]
Concentration risk investment portfolio	7.00%	6.00%