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Subsequent Events - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands |  |  |  |  |  | 9 Months Ended |  |  |  |  |  |
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Nov. 03, 2025 | Oct. 22, 2025 | Oct. 20, 2025 | Oct. 16, 2025 | Oct. 03, 2025 | Sep. 30, 2025 | Sep. 30, 2024 | Oct. 24, 2025 | Oct. 21, 2025 | Oct. 17, 2025 | Oct. 14, 2025 | Oct. 01, 2025 | Dec. 31, 2024
Subsequent Event [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  | $ 191,000 |  |  |  |  |  |  |  | $ 175,000 |
Credit facility, interest rate per annum |  |  |  |  |  |  | 1.092% |  | 0.696% |  |  |  |  |  |  |
Investments at cost |  |  |  |  |  |  | $ 1,169,390 | [1],[2],[3] |  |  |  |  |  |  | $ 1,075,157 | [4],[5],[6]
Investment, Type [Extensible Enumeration] |  |  |  |  |  |  | Pfanstiehl Inc [Member] |  |  |  |  |  |  |  | Pfanstiehl Inc [Member] |
First Lien Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investments at cost | [7] |  |  |  |  |  | $ 856,304 |  |  |  |  |  |  |  | $ 729,084 |
Subsequent Events | Bobcat Connecticut LLC | First Lien Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investments at cost |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 16,000 |  |
Subsequent Events | Bobcat Connecticut LLC | Common Equity |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investments at cost |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,000 |  |
Subsequent Events | GPS Insight, Inc. | First Lien Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investments at cost |  |  |  |  |  |  |  |  |  |  |  | $ 23,201 |  |  |  |
Subsequent Events | Aldinger Company |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investment, Type [Extensible Enumeration] |  |  |  | Common and Preferred Equity Investments [Member] |  |  |  |  |  |  |  |  |  |  |  |
Realized gain (loss) on investments |  |  |  | $ 2,327 |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Events | GP&C Operations, LLC (dba Garlock Printing and Converting) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investment, Type [Extensible Enumeration] |  |  | Common Equity |  |  |  |  |  |  |  |  |  |  |  |  |
Realized gain (loss) on investments |  |  | $ 600 |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Events | AmeriWater LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investments at cost |  |  |  |  |  |  |  |  |  | $ 2,511 |  |  |  |  |  |
Investment, Type [Extensible Enumeration] |  |  |  |  |  |  |  |  |  | Subordinated Debt [Member] |  |  |  |  |  |
Maximum | Subsequent Events | Bobcat Connecticut LLC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Unfunded commitment |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 250 |  |
March 2030 Notes | Subsequent Events |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  | $ 100,000 |  |  |  |  |  |  |  |  |  |
Debt Instrument Outstanding Principal |  |  |  |  |  | $ 200,000 |  |  |  |  |  |  |  |  |  |
4.74% Fixed Interest Rate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  | $ 5,000 |  |  |  |  |  |  |  |  |
January 2026 Notes | Subsequent Events |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument redemption principle percentage |  | 100.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument redemption of outstanding amount |  | $ 100,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument redemption price |  | $ 101,227 |  |  |  |  |  |  |  |  |  |  |  |  |  |
SBA Debentures | 4.74% Fixed Interest Rate | Subsequent Events |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument issued amount |  |  |  |  |  |  |  |  |  |  |  |  | $ 3,500 |  |  |
Interest rate |  |  |  |  |  |  |  |  |  |  |  |  | 4.74% |  |  |
SBA Debentures | 4.73% Fixed Interest Rate | Subsequent Events |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument issued amount |  |  |  |  |  |  |  |  |  |  | $ 13,000 |  |  |  |  |
Interest rate |  |  |  |  |  |  |  |  |  |  | 4.73% |  |  |  |  |
SPV Credit Facility | SPV Credit Agreement | Subsequent Events | Western Alliance Trust Company |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Credit facility amount |  |  |  |  | $ 175,000 |  |  |  |  |  |  |  |  |  |  |
Credit facility, interest rate per annum |  |  |  |  | 0.11448% |  |  |  |  |  |  |  |  |  |  |
Credit facility commitment percentage |  |  |  |  | 65.00% |  |  |  |  |  |  |  |  |  |  |
Remaining unused portion of Credit Facility commitment percentage |  |  |  |  | 0.50% |  |  |  |  |  |  |  |  |  |  |
Percentage of equity interest |  |  |  |  | 100.00% |  |  |  |  |  |  |  |  |  |  |
SPV Credit Facility | SPV Credit Agreement | Minimum | Subsequent Events | Western Alliance Trust Company |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Credit facility, interest rate per annum |  |  |  |  | 2.50% |  |  |  |  |  |  |  |  |  |  |
SPV Credit Facility | SPV Credit Agreement | Maximum | Subsequent Events | Western Alliance Trust Company |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Credit facility amount |  |  |  |  | $ 250,000 |  |  |  |  |  |  |  |  |  |  |
Credit facility, interest rate per annum |  |  |  |  | 2.675% |  |  |  |  |  |  |  |  |  |  |
Credit facility commitment percentage |  |  |  |  | 35.00% |  |  |  |  |  |  |  |  |  |  |
Regular Dividend | Subsequent Events |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends to stockholders |  | $ 0.43 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Supplemental Dividends | Subsequent Events |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends to stockholders |  | $ 0.07 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Quarterly Dividends | Subsequent Events |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividend payable date |  | Dec. 29, 2025 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividend record date |  | Dec. 19, 2025 |  |  |  |  |  |  |  |  |  |  |  |  |  |
[1] | (a) See Note 3 to the consolidated financial statements for portfolio composition by geographic location.
[2] | (b) Equity ownership may be held in shares or units of companies related to the portfolio companies. The Company’s investments are generally classified as “restricted securities”, unless otherwise noted, as such term is defined under Regulation S-X Rule 6-03(f) or Securities Act Rule 144. As of September 30, 2025, the Company held restricted securities with an aggregate fair value of $1,192,748, or 168% of the Company's net assets.
[3] | (c) All debt investments are income producing, unless otherwise indicated. Equity investments are non-income producing unless otherwise noted.
[4] | (a) See Note 3 to the consolidated financial statements for portfolio composition by geographic location.
[5] | (b) Equity ownership may be held in shares or units of companies related to the portfolio companies.
[6] | (c) All debt investments are income producing, unless otherwise indicated. Equity investments are non-income producing unless otherwise noted.
[7] |
(1) | Includes unitranche investments, which account for 46.7% and 47.7% of the Company's portfolio on a fair value and cost basis as of September 30, 2025, respectively. Includes unitranche investments, which account for 39.9% and 40.4% of the Company's portfolio on a fair value and cost basis as of December 31, 2024, respectively.

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