Debt - Additional Information (Details) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | 9 Months Ended | 12 Months Ended | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Jun. 01, 2029 |
Jun. 29, 2026 |
May 29, 2026 |
Dec. 22, 2025 |
Nov. 03, 2025 |
Oct. 03, 2025 |
May 21, 2025 |
Mar. 19, 2025 |
Oct. 08, 2021 |
Dec. 23, 2020 |
Apr. 24, 2019 |
Sep. 30, 2026 |
Sep. 30, 2025 |
Jun. 30, 2025 |
Sep. 30, 2026 |
Sep. 30, 2025 |
Dec. 31, 2025 |
Oct. 16, 2025 |
Jul. 25, 2024 |
|
| Debt Instrument [Line Items] | |||||||||||||||||||
| Debt instrument asset coverage percentage | 283.20% | 276.30% | |||||||||||||||||
| Aggregate principal amount | $ 289,500 | $ 289,500 | $ 237,500 | ||||||||||||||||
| Weighted average interest rate | 5.813% | 4.857% | 5.813% | 4.857% | |||||||||||||||
| Net proceeds from the notes | $ 120,000 | $ 100,000 | |||||||||||||||||
| Unamortized deferred financing costs | $ 15,602 | 15,602 | 14,275 | ||||||||||||||||
| Loss on extinguishment of debt | (268) | $ (304) | (579) | $ (630) | |||||||||||||||
| Secured borrowings | 10,460 | 10,460 | 12,000 | ||||||||||||||||
| Aggregate amount of outstanding of senior securities | 422,710 | 420,850 | |||||||||||||||||
| Fair value of loans included in investments | 10,354 | 10,354 | 11,995 | ||||||||||||||||
| Available borrowings under the Credit Facility | $ 132,750 | $ 132,750 | $ 141,150 | ||||||||||||||||
| Minimum utilization amount commitments description | The SPV pays a commitment fee that varies depending on the size of the unused portion of the SPV Credit Facility: (1) if the utilized portion of the aggregate commitments as of the close of business on such day is less than 35% of the aggregate commitments (the “Minimum Utilization Amount”), the commitment fee will equal the sum of (a) the then applicable margin multiplied by (i) the Minimum Utilization Amount minus (ii) the aggregate outstanding principal balance of the advances on such day and (b) 0.50% multiplied by 65% of the commitments and (2) if the utilized portion of the aggregate commitments is greater than or equal to the Minimum Utilization Amount, the commitment fee will equal 0.50% multiplied by the unused amount of the commitments. | ||||||||||||||||||
| Secured Borrowings | |||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||
| Weighted average interest rate | 7.846% | 8.242% | 7.846% | 8.242% | 7.90% | ||||||||||||||
| Small Business Administration Debentures [Member] | |||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||
| Weighted average interest rate | 4.592% | 4.139% | 4.592% | 4.139% | |||||||||||||||
| Unamortized deferred financing costs | $ 7,651 | $ 7,651 | $ 6,943 | ||||||||||||||||
| Prepayment of debentures | 17,000 | $ 16,500 | $ 24,000 | $ 28,500 | |||||||||||||||
| Debt instrument, maturity year range, start | 2032 | ||||||||||||||||||
| Debt instrument, maturity year range, end | 2033 | 2033 | |||||||||||||||||
| Loss on extinguishment of debt | (268) | $ (304) | $ (579) | $ (630) | |||||||||||||||
| Debt instrument term | 10 years | ||||||||||||||||||
| Interest rate payment term | semi-annually on March 1 and September 1 | ||||||||||||||||||
| Unused commitments amount | 8,000 | $ 8,000 | 84,000 | ||||||||||||||||
| 4.75% Notes due 2026 | |||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||
| Maturity date | Jan. 31, 2026 | ||||||||||||||||||
| Aggregate principal amount | $ 125,000 | $ 125,000 | |||||||||||||||||
| Interest rate | 4.75% | ||||||||||||||||||
| Net proceeds from the notes | $ 122,134 | ||||||||||||||||||
| Underwriting discounts | $ 2,500 | ||||||||||||||||||
| Percentage of public offering price | 100.00% | ||||||||||||||||||
| Unamortized deferred financing costs | $ 366 | ||||||||||||||||||
| Loss on extinguishment of debt | $ 112 | (75) | |||||||||||||||||
| Debt instrument, redemption description | The maturity date of the January 2026 Notes was January 31, 2026 and the January 2026 Notes bore interest at a rate of 4.75%. On May 21, 2025, the Company redeemed $25,000 of the $125,000 aggregate principal amount on the January 2026 Notes, resulting in a realized loss on extinguishment of debt of $75. On November 3, 2025, the Company fully redeemed the remaining $100,000 in aggregate principal amount of the January 2026 Notes, resulting in a realized loss on extinguishment of debt of $112. | ||||||||||||||||||
| Debt instrument redemption of aggregate principal amount | $ 100,000 | $ 25,000 | |||||||||||||||||
| 3.50% Notes Due 2026 | |||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||
| Maturity date | Nov. 15, 2026 | ||||||||||||||||||
| Aggregate principal amount | $ 125,000 | ||||||||||||||||||
| Interest rate | 3.50% | ||||||||||||||||||
| Net proceeds from the notes | $ 122,177 | ||||||||||||||||||
| Underwriting discounts | $ 2,500 | ||||||||||||||||||
| Percentage of public offering price | 99.996% | ||||||||||||||||||
| Unamortized deferred financing costs | $ 318 | ||||||||||||||||||
| Loss on extinguishment of debt | $ 194 | ||||||||||||||||||
| Debt instrument redemption of aggregate principal amount | $ 125,000 | ||||||||||||||||||
| 6.75% Notes Due 2030 | |||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||
| Maturity date | Mar. 19, 2030 | ||||||||||||||||||
| Aggregate principal amount | $ 100,000 | $ 100,000 | |||||||||||||||||
| Interest rate | 6.75% | 6.75% | |||||||||||||||||
| Net proceeds from the notes | $ 98,876 | $ 96,946 | |||||||||||||||||
| Underwriting discounts | $ 1,500 | $ 2,000 | |||||||||||||||||
| Percentage of public offering price | 100.705% | 99.29954% | |||||||||||||||||
| Unamortized deferred financing costs | $ 329 | $ 354 | |||||||||||||||||
| Debt instrument, redemption description | The March 2030 Notes may be redeemed in whole or in part at any time or from time to time at the Company’s option subject to a make whole provision if redeemed before September 19, 2029 (the date falling six months prior to maturity) and at par thereafter. Interest on the March 2030 Notes is payable on March 19 and September 19 of each year. | ||||||||||||||||||
| 6.625% Notes Due 2029 | |||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||
| Maturity date | Jun. 01, 2029 | ||||||||||||||||||
| Aggregate principal amount | $ 120,000 | ||||||||||||||||||
| Interest rate | 6.625% | 6.625% | |||||||||||||||||
| Net proceeds from the notes | $ 117,490 | ||||||||||||||||||
| Underwriting discounts | $ 1,500 | ||||||||||||||||||
| Percentage of public offering price | 99.45% | ||||||||||||||||||
| Unamortized deferred financing costs | 350 | $ 350 | |||||||||||||||||
| Debt instrument, redemption description | The June 2029 Notes may be redeemed in whole or in part at any time or from time to time at the Company’s option subject to a make whole provision if redeemed before March 1, 2029 (the date falling three months prior to maturity) and at par thereafter. In connection with the issuance and sale of the June 2029 Notes, the Company entered into a registration rights agreement, dated as of May 29, 2026 (the “Registration Rights Agreement”), with the institutional purchasers (the “Purchasers”). Pursuant to the Registration Rights Agreement, the Company filed with the SEC a registration statement, and, on September 16, 2026, commenced an offer to exchange the June 2029 Notes initially issued in the private placement on May 29, 2026 for a like principal amount of the June 2029 Notes registered under the Securities Act with terms substantially identical to those of the June 2029 Notes issued in the private placement (except for provisions relating to transfer restrictions and payment of additional interest). The offer to exchange the June 2029 Notes expired on October 16, 2026 and was completed promptly thereafter. The Company does not intend to list the June 2029 Notes on any securities exchange or automated dealer quotation system. See Note 11. Subsequent Events, for more information. | ||||||||||||||||||
| 2026 Notes | |||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||
| Debt instrument redemption of issued and outstanding amount | 125,000 | $ 125,000 | |||||||||||||||||
| Credit And Security Agreement [Member] | Western Alliance Trust Company [Member] | Special Purpose Vehicle Credit Facility [Member] | |||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||
| Maturity date | Oct. 16, 2030 | ||||||||||||||||||
| Interest rate | 0.11448% | ||||||||||||||||||
| Debt Instrument, Variable Interest Rate, Type [Extensible Enumeration] | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member] | ||||||||||||||||||
| Percentage of equity interest | 100.00% | ||||||||||||||||||
| Credit Facility commitment | $ 225,000 | $ 175,000 | |||||||||||||||||
| Accordion feature for an increase of credit facility commitment | $ 250,000 | ||||||||||||||||||
| Reinvestment period final date | Oct. 16, 2029 | ||||||||||||||||||
| Available borrowings under the Credit Facility | $ 91,122 | $ 91,122 | $ 102,208 | ||||||||||||||||
| Credit And Security Agreement [Member] | Western Alliance Trust Company [Member] | Maximum | Special Purpose Vehicle Credit Facility [Member] | |||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||
| Interest rate | 2.675% | ||||||||||||||||||
| Credit facility commitment percentage | 35.00% | ||||||||||||||||||
| Credit And Security Agreement [Member] | Western Alliance Trust Company [Member] | Minimum | Special Purpose Vehicle Credit Facility [Member] | |||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||
| Interest rate | 2.50% | ||||||||||||||||||
| March 2030 Notes | |||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||
| Debt instrument outstanding principal | $ 200,000 | ||||||||||||||||||
| Revolving Credit Facility | Senior Secured Revolving Credit Agreement [Member] | ING Capital LLC | |||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||
| Credit facility commitment percentage | 35.00% | ||||||||||||||||||
| Percentage of equity interest | 35.00% | ||||||||||||||||||
| Credit Facility commitment | $ 140,000 | ||||||||||||||||||
| Revolving Credit Facility | Senior Secured Revolving Credit Agreement [Member] | ING Capital LLC | Maximum | |||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||
| Credit facility, interest rate per annum | 2.675% | ||||||||||||||||||
| Remaining unused portion of Credit Facility commitment percentage | 0.50% | ||||||||||||||||||
| Revolving Credit Facility | Senior Secured Revolving Credit Agreement [Member] | ING Capital LLC | Minimum | |||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||
| Credit facility, interest rate per annum | 2.50% | ||||||||||||||||||