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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
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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% |

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