| Fair Value, Assets Measured on Recurring Basis [Table Text Block] |
| | | June 30, 2026 | |
| | | Level 1 | | | Level 2 | | | Level 3 | | | Total | |
| | | (In thousands) | |
| Debt investments | | $ | — | | | $ | — | | | $ | 647,999 | | | $ | 647,999 | |
| Warrant investments | | | — | | | | 2,590 | | | | 14,113 | | | | 16,703 | |
| Other investments | | | — | | | | — | | | | 4,037 | | | | 4,037 | |
| Equity investments | | | 1,875 | | | | — | | | | 5,882 | | | | 7,757 | |
| Equity interest in RoHo Joint Venture (1) | | | — | | | | — | | | | — | | | | 215 | |
| Total investments | | $ | 1,875 | | | $ | 2,590 | | | $ | 672,031 | | | $ | 676,711 | |
| | | December 31, 2025 | |
| | | Level 1 | | | Level 2 | | | Level 3 | | | Total | |
| | | (In thousands) | |
| Debt investments | | $ | — | | | $ | — | | | $ | 596,025 | | | $ | 596,025 | |
| Warrant investments | | | — | | | | 1,916 | | | | 14,732 | | | | 16,648 | |
| Other investments | | | — | | | | — | | | | 3,444 | | | | 3,444 | |
| Equity investments | | | 3,988 | | | | — | | | | 27,139 | | | | 31,127 | |
| Total investments | | $ | 3,988 | | | $ | 1,916 | | | $ | 641,340 | | | $ | 647,244 | |
|
| Fair Value Measurement Inputs and Valuation Techniques [Table Text Block] |
| June 30, 2026 | |
| | | Fair | | Valuation Techniques/ | | Unobservable | | | | Weighted | |
| Investment Type | | Value | | Methodologies | | Input | | Range | | Average(1) | |
| | | | | | (Dollars in thousands, except per share data) | | | | | | |
| Debt investments | | $ | 581,983 | | Discounted Expected Future Cash Flows | | Hypothetical Market Yield | | 9% – 20% | | | 12 | % |
| | | | | | | | | | | | | | |
| | | | 66,016 | | Multiple Probability Weighted Cash Flow Model | | Probability Weighting | | 5% – 100% | | | 50 | % |
| | | | | | | | | | | | | | |
| Warrant investments | | | 14,113 | | Black-Scholes Valuation Model | | Asset Value Per Share | | $0.00 – $807.91 | | $ | 11.94 | |
| | | | | | | | Average Industry Volatility | | 24% | | | 24 | % |
| | | | | | | | Marketability Discount | | 0% – 20% | | | 20 | % |
| | | | | | | | Estimated Time to Exit (in years) | | 1 to 5 | | | 3 | |
| | | | | | | | | | | | | | |
| Other investments | | | 4,037 | | Multiple Probability Weighted Cash Flow Model | | Discount Rate | | 10% – 100% | | | 40 | % |
| | | | | | | | Probability Weighting | | 100% | | | 100 | % |
| | | | | | | | | | | | | | |
| Equity investments | | | 5,882 | | Last Equity Financing | | Price Per Share | | $0.06 – $1,000.00 | | $ | 663.72 | |
| | | | | | | | Discount Rate | | 0% – 20% | | | 13 | % |
| | | | | | | | | | | | | | |
| | | | — | | Scenario Model | | Probability Weighting | | 100% | | | 100 | % |
| | | | | | | | | | | | | | |
| Total Level 3 investments | | $ | 672,031 | | | | | | | | | | |
| December 31, 2025 | |
| | | Fair | | Valuation Techniques/ | | Unobservable | | | | Weighted | |
| Investment Type | | Value | | Methodologies | | Input | | Range | | Average(1) | |
| | | | | | (Dollars in thousands, except per share data) | | | | | | |
| Debt investments | | $ | 558,294 | | Discounted Expected Future Cash Flows | | Hypothetical Market Yield | | 11% – 20% | | | 13 | % |
| | | | | | | | | | | | | | |
| | | | 37,731 | | Multiple Probability Weighted Cash Flow Model | | Probability Weighting | | 30% – 100% | | | 56 | % |
| | | | | | | | | | | | | | |
| Warrant investments | | | 14,732 | | Black-Scholes Valuation Model | | Asset Value Per Share | | $0.00 – $807.91 | | $ | 13.72 | |
| | | | | | | | Average Industry Volatility | | 24% | | | 24 | % |
| | | | | | | | Marketability Discount | | 0 – 20% | | | 20 | % |
| | | | | | | | Estimated Time to Exit (in years) | | 1 to 5 | | | 3 | |
| | | | | | | | | | | | | | |
| Other investments | | | 3,444 | | Multiple Probability Weighted Cash Flow Model | | Discount Rate | | 20% – 100% | | | 44 | % |
| | | | | | | | Probability Weighting | | 0% – 100% | | | 100 | % |
| | | | | | | | | | | | | | |
| Equity investments | | | 27,139 | | Last Equity Financing | | Price Per Share | | $0.06 – $1,000.00 | | $ | 186.54 | |
| | | | | | | | | | | | | | |
| | | | — | | Scenario Model | | Probability Weighting | | 100% | | | 100 | % |
| | | | | | | | | | | | | | |
| Total Level 3 investments | | $ | 641,340 | | | | | | | | | | |
|
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] |
| | | Three months ended June 30, 2026 | |
| | | Debt | | | Warrant | | | Equity | | | Other | | | | | |
| | | Investments | | | Investments | | | Investments | | | Investments | | | Total | |
| | | (In thousands) | |
| Level 3 assets, beginning of period | | $ | 645,629 | | | $ | 14,994 | | | $ | 27,139 | | | $ | 3,664 | | | $ | 691,426 | |
| Purchase of investments | | | 72,762 | | | | — | | | | — | | | | — | | | | 72,762 | |
| Warrants received and classified as Level 3 | | | | | | | 247 | | | | — | | | | — | | | | 247 | |
| Principal payments received on investments | | | (46,859 | ) | | | — | | | | — | | | | (264 | ) | | | (47,123 | ) |
| PIK interest on investments | | | 1,566 | | | | — | | | | — | | | | — | | | | 1,566 | |
| Proceeds from sale of investments | | | (1 | ) | | | (1,229 | ) | | | (622 | ) | | | (52 | ) | | | (1,904 | ) |
| Net realized gain (loss) on investments | | | 1 | | | | 955 | | | | 200 | | | | (7,278 | ) | | | (6,122 | ) |
| Unrealized (depreciation) appreciation included in earnings | | | (25,005 | ) | | | (431 | ) | | | (20,712 | ) | | | 7,510 | | | | (38,638 | ) |
| Transfer out of Level 3 | | | — | | | | (89 | ) | | | — | | | | — | | | | (89 | ) |
| Transfer out of warrant and equity investments | | | — | | | | (334 | ) | | | (123 | ) | | | 457 | | | | — | |
| Other | | | (94 | ) | | | — | | | | — | | | | — | | | | (94 | ) |
| Level 3 assets, end of period | | $ | 647,999 | | | $ | 14,113 | | | $ | 5,882 | | | $ | 4,037 | | | $ | 672,031 | |
| | | Three months ended June 30, 2025 | |
| | | Debt | | | Warrant | | | Equity | | | Other | | | | | |
| | | Investments | | | Investments | | | Investments | | | Investments | | | Total | |
| | | (In thousands) | |
| Level 3 assets, beginning of period | | $ | 643,567 | | | $ | 17,159 | | | $ | 12,974 | | | $ | 13,697 | | | $ | 687,397 | |
| Purchase of investments | | | 42,225 | | | | — | | | | 144 | | | | — | | | | 42,369 | |
| Warrants received and classified as Level 3 | | | — | | | | 117 | | | | — | | | | — | | | | 117 | |
| Principal payments received on investments | | | (78,493 | ) | | | — | | | | — | | | | — | | | | (78,493 | ) |
| PIK interest on investments | | | 243 | | | | — | | | | — | | | | — | | | | 243 | |
| Proceeds from sale of investments | | | (1 | ) | | | (579 | ) | | | (203 | ) | | | — | | | | (783 | ) |
| Net realized (loss) gain on investments | | | (9,364 | ) | | | (99 | ) | | | 169 | | | | — | | | | (9,294 | ) |
| Unrealized (depreciation) appreciation included in earnings | | | (18,005 | ) | | | 3,858 | | | | (172 | ) | | | (7,339 | ) | | | (21,658 | ) |
| Transfer out of debt investments | | | (2,093 | ) | | | — | | | | — | | | | 2,093 | | | | — | |
| Other | | | 1,092 | | | | — | | | | — | | | | — | | | | 1,092 | |
| Level 3 assets, end of period | | $ | 579,171 | | | $ | 20,456 | | | $ | 12,912 | | | $ | 8,451 | | | $ | 620,990 | |
| | | Six months ended June 30, 2026 | |
| | | Debt | | | Warrant | | | Equity | | | Other | | | | | |
| | | Investments | | | Investments | | | Investments | | | Investments | | | Total | |
| | | (In thousands) | |
| Level 3 assets, beginning of period | | $ | 596,025 | | | $ | 14,732 | | | $ | 27,139 | | | $ | 3,444 | | | $ | 641,340 | |
| Purchase of investments | | | 162,766 | | | | — | | | | — | | | | — | | | | 162,766 | |
| Warrants received and classified as Level 3 | | | — | | | | 618 | | | | — | | | | — | | | | 618 | |
| Principal payments received on investments | | | (84,749 | ) | | | — | | | | — | | | | (422 | ) | | | (85,171 | ) |
| PIK interest on investments | | | 2,844 | | | | — | | | | — | | | | — | | | | 2,844 | |
| Proceeds from sale of investments | | | (1 | ) | | | (1,230 | ) | | | (641 | ) | | | (136 | ) | | | (2,008 | ) |
| Net realized gain (loss) on investments | | | 2 | | | | 690 | | | | 219 | | | | (7,194 | ) | | | (6,283 | ) |
| Unrealized (depreciation) appreciation included in earnings | | | (27,965 | ) | | | (274 | ) | | | (20,712 | ) | | | 7,888 | | | | (41,063 | ) |
| Transfer out of Level 3 | | | — | | | | (89 | ) | | | — | | | | — | | | | (89 | ) |
| Transfer out of warrant and equity investments | | | — | | | | (334 | ) | | | (123 | ) | | | 457 | | | | — | |
| Other | | | (923 | ) | | | — | | | | — | | | | — | | | | (923 | ) |
| Level 3 assets, end of period | | $ | 647,999 | | | $ | 14,113 | | | $ | 5,882 | | | $ | 4,037 | | | $ | 672,031 | |
| | | Six months ended June 30, 2025 | |
| | | Debt | | | Warrant | | | Equity | | | Other | | | | | |
| | | Investments | | | Investments | | | Investments | | | Investments | | | Total | |
| | | (In thousands) | |
| Level 3 assets, beginning of period | | $ | 638,779 | | | $ | 16,438 | | | $ | 25,611 | | | $ | 14,637 | | | $ | 695,465 | |
| Purchase of investments | | | 113,854 | | | | — | | | | 2,189 | | | | 15 | | | | 116,058 | |
| Warrants received and classified as Level 3 | | | — | | | | 282 | | | | — | | | | — | | | | 282 | |
| Principal payments received on investments | | | (129,238 | ) | | | — | | | | — | | | | — | | | | (129,238 | ) |
| PIK interest on investments | | | 528 | | | | — | | | | — | | | | — | | | | 528 | |
| Proceeds from sale of investments | | | (2 | ) | | | (579 | ) | | | (203 | ) | | | — | | | | (784 | ) |
| Net realized (loss) gain on investments | | | (9,363 | ) | | | (99 | ) | | | 169 | | | | — | | | | (9,293 | ) |
| Unrealized (depreciation) appreciation included in earnings | | | (34,811 | ) | | | 4,414 | | | | (14,854 | ) | | | (8,294 | ) | | | (53,545 | ) |
| Transfer out of warrant investments | | | (2,093 | ) | | | — | | | | — | | | | 2,093 | | | | — | |
| Other | | | 1,517 | | | | — | | | | — | | | | — | | | | 1,517 | |
| Level 3 assets, end of period | | $ | 579,171 | | | $ | 20,456 | | | $ | 12,912 | | | $ | 8,451 | | | $ | 620,990 | |
|