| Investments in and Advances to Affiliates [Table Text Block] |
| | | | | | | | | | | Three months ended March 31, 2026 | | | | | | | | | | | | | |
| | | Fair value at | | | | | | | | | | | | | | | Transfers | | | | | | | Net | | | | | | | Fair value at | | | | | |
| Portfolio | | December 31, | | | | | | | Principal | | | | | | | in/(out) at | | | Discount | | | unrealized | | | Net realized | | | March 31, | | | Interest | |
| Company | | 2025 | | | Purchases | | | payments | | | PIK | | | fair value | | | accretion | | | gain/(loss) | | | gain/(loss) | | | 2026 | | | income | |
| | | (In thousands) | |
| Aulea Medical, Inc. | | $ | — | | | $ | — | | | $ | — | | | $ | — | | | $ | — | | | $ | — | | | $ | — | | | | | | | $ | — | | | $ | — | |
| Evelo Biosciences, Inc. | | | 1,486 | | | | — | | | | — | | | | — | | | | — | | | | — | | | | | | | | — | | | | 1,486 | | | | — | |
| Hound Labs II LLC | | | 11,369 | | | | — | | | | — | | | | 219 | | | | — | | | | — | | | | (15 | ) | | | — | | | | 11,573 | | | | 219 | |
| Nexii, Inc. | | | — | | | | 4 | | | | — | | | | — | | | | — | | | | — | | | | (4 | ) | | | — | | | | — | | | | 27 | |
| NextCar Holding Company, Inc. | | | 1,079 | | | | — | | | | (243 | ) | | | — | | | | — | | | | — | | | | 169 | | | | — | | | | 1,005 | | | | 55 | |
| Shengrow Inc. | | | 49,210 | | | | — | | | | — | | | | 622 | | | | — | | | | 306 | | | | — | | | | — | | | | 50,138 | | | | 1,271 | |
| Total non-controlled affiliates | | $ | 63,144 | | | $ | 4 | | | $ | (243 | ) | | $ | 841 | | | $ | — | | | $ | 306 | | | $ | 150 | | | $ | — | | | $ | 64,202 | | | $ | 1,572 | |
| | | | | | | | | | | Three months ended March 31, 2025 | | | | | | | | | | | | | |
| | | Fair value at | | | | | | | | | | | | | | Transfers | | | | | | | Net | | | | | | | Fair value at | | | | | |
| Portfolio | | December 31, | | | | | | | | | | | | | | in/(out) at | | | Discount | | | unrealized | | | Net realized | | | March 31, | | | Interest | |
| Company | | 2024 | | | Purchases | | | Sales | | | PIK | | | fair value | | | accretion | | | gain/(loss) | | | gain/(loss) | | | 2025 | | | income | |
| | | (In thousands) | |
| Aulea Medical, Inc. | | $ | — | | | $ | — | | | $ | — | | | $ | — | | | $ | — | | | $ | — | | | $ | — | | | $ | — | | | $ | — | | | $ | — | |
| Evelo Biosciences, Inc. | | | 8,307 | | | | 2 | | | | — | | | | — | | | | — | | | | — | | | | (2 | ) | | | — | | | | 8,307 | | | | — | |
| Total non-controlled affiliates | | $ | 8,307 | | | $ | 2 | | | $ | — | | | $ | — | | | $ | — | | | $ | — | | | $ | (2 | ) | | $ | — | | | $ | 8,307 | | | $ | — | |
| | | | | | | | | | | Three months ended March 31, 2025 | | | | | | | | | | | | | |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| | | Fair value at | | | | | | | | | | | | Transfers | | | | | | Net | | | | | | Fair value at | | | Interest | |
| Portfolio | | December 31, | | | | | | | Principal | | | | | | | in/(out) at | | | Discount | | | unrealized | | | Net realized | | | March 31, | | | income | |
| Company | | 2024 | | | Purchases | | | payments | | | PIK | | | fair value | | | accretion | | | gain/(loss) | | | gain/(loss) | | | 2025 | | | (reversal) | |
| | | (In thousands) | |
| Better Place Forests Co. | | $ | — | | | $ | 941 | | | $ | — | | | $ | — | | | $ | — | | | $ | — | | | $ | (62 | ) | | $ | — | | | $ | 879 | | | $ | — | |
| HIMV LLC | | | 6,230 | | | | — | | | | — | | | | — | | | | — | | | | — | | | | (940 | ) | | | — | | | | 5,290 | | | | — | |
| Nexii, Inc. | | | 8,547 | | | | — | | | | — | | | | — | | | | — | | | | — | | | | 153 | | | | — | | | | 8,700 | | | | 20 | |
| Swift Health Systems, Inc. | | | 17,042 | | | | 2,009 | | | | — | | | | 208 | | | | — | | | | 9 | | | | (19,268 | ) | | | — | | | | — | | | | (81 | ) |
| Total controlled affiliates | | $ | 31,819 | | | $ | 2,950 | | | $ | — | | | $ | 208 | | | $ | — | | | $ | 9 | | | $ | (20,117 | ) | | $ | — | | | $ | 14,869 | | | $ | (61 | ) |
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