| Schedule of Debt [Table Text Block] |
| | | December 31, 2025 | | | December 31, 2024 | |
| | | Total | | | Balance | | | Unused | | | Total | | | Balance | | | Unused | |
| | | Commitment | | | Outstanding | | | Commitment | | | Commitment | | | Outstanding | | | Commitment | |
| | | (In thousands) | |
| Key Facility | | $ | 150,000 | | | $ | — | | | $ | 150,000 | | | $ | 150,000 | | | $ | — | | | $ | 150,000 | |
| NYL Facility | | | 250,000 | | | | 181,000 | | | | 69,000 | | | | 250,000 | | | | 181,000 | | | | 69,000 | |
| Nuveen Facility | | | 200,000 | | | | 90,000 | | | | 110,000 | | | | 100,000 | | | | 75,000 | | | | 25,000 | |
| 2022 Asset-Backed Notes | | | — | | | | — | | | | — | | | | 81,078 | | | | 81,078 | | | | — | |
| 2028 Notes | | | 57,500 | | | | 57,500 | | | | — | | | | — | | | | — | | | | — | |
| 2027 Notes | | | 57,500 | | | | 57,500 | | | | — | | | | 57,500 | | | | 57,500 | | | | — | |
| 2026 Notes | | | 57,500 | | | | 57,500 | | | | — | | | | 57,500 | | | | 57,500 | | | | — | |
| 2030 Convertible Notes | | | 31,500 | | | | 31,500 | | | | — | | | | — | | | | — | | | | — | |
| 2031 Convertible Notes | | | 2,750 | | | | 2,750 | | | | — | | | | 20,000 | | | | 20,000 | | | | — | |
| Total before debt issuance costs | | | 806,750 | | | | 477,750 | | | | 329,000 | | | | 716,078 | | | | 472,078 | | | | 244,000 | |
| Unamortized debt issuance costs attributable to term borrowings | | | — | | | | (4,723 | ) | | | — | | | | — | | | | (4,174 | ) | | | — | |
| Total borrowings outstanding, net | | $ | 806,750 | | | $ | 473,027 | | | $ | 329,000 | | | $ | 716,078 | | | $ | 467,904 | | | $ | 244,000 | |
|
| Schedule of Long-Term Debt Instruments [Table Text Block] |
| | | Total Amount | | | | | | | | | | | | | |
| | | Outstanding | | | | | | | Involuntary | | | Average | |
| | | Exclusive of | | | Asset | | | Liquidation | | | Market | |
| | | Treasury | | | Coverage | | | Preference | | | Value per | |
| Class and Year | | Securities(1) | | | per Unit(2) | | | per Unit(3) | | | Unit(4) | |
| | | (In thousands, except unit data) | |
| Credit facilities | | | | | | | | | | | | | | | | |
| 2025 | | $ | 271,000 | | | $ | 2,938 | | | | — | | | | N/A | |
| 2024 | | $ | 256,000 | | | $ | 3,157 | | | | — | | | | N/A | |
| 2023 | | $ | 251,000 | | | $ | 3,147 | | | | — | | | | N/A | |
| 2022 | | $ | 181,750 | | | $ | 4,169 | | | | — | | | | N/A | |
| 2021 | | $ | 132,250 | | | $ | 3,823 | | | | — | | | | N/A | |
| 2020 | | $ | 50,250 | | | $ | 7,965 | | | | — | | | | N/A | |
| 2019 | | $ | 17,000 | | | $ | 19,908 | | | | — | | | | N/A | |
| 2018 | | $ | 90,500 | | | $ | 2,896 | | | | — | | | | N/A | |
| 2017 | | $ | 58,000 | | | $ | 3,973 | | | | — | | | | N/A | |
| 2016 | | $ | 63,000 | | | $ | 3,733 | | | | — | | | | N/A | |
| 2031 Convertible Notes | | | | | | | | | | | | | | | | |
| 2025 | | $ | 2,750 | | | $ | 289,546 | | | | — | | | | N/A | |
| 2024 | | $ | 20,000 | | | $ | 40,413 | | | | — | | | | N/A | |
| 2023 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2022 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2021 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2020 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2019 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2018 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2017 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2016 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2030 Convertible Notes | | | | | | | | | | | | | | | | |
| 2025 | | $ | 31,500 | | | $ | 25,278 | | | | — | | | | N/A | |
| 2024 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2023 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2022 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2021 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2020 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2019 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2018 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2017 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2016 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2028 Notes | | | | | | | | | | | | | | | | |
| 2025 | | $ | 57,500 | | | $ | 13,848 | | | | — | | | | N/A | |
| 2024 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2023 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2022 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2021 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2020 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2019 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2018 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2017 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2016 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2027 Notes | | | | | | | | | | | | | | | | |
| 2025 | | $ | 57,500 | | | $ | 13,848 | | | | — | | | $ | 24.65 | |
| 2024 | | $ | 57,500 | | | $ | 14,057 | | | | — | | | $ | 24.13 | |
| 2023 | | $ | 57,500 | | | $ | 13,739 | | | | — | | | $ | 24.26 | |
| 2022 | | $ | 57,500 | | | $ | 13,179 | | | | — | | | $ | 24.09 | |
| 2021 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2020 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2019 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2018 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2017 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2016 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2026 Notes | | | | | | | | | | | | | | | | |
| 2025 | | $ | 57,500 | | | $ | 13,848 | | | | — | | | $ | 24.92 | |
| 2024 | | $ | 57,500 | | | $ | 14,057 | | | | — | | | $ | 24.27 | |
| 2023 | | $ | 57,500 | | | $ | 13,739 | | | | — | | | $ | 23.75 | |
| 2022 | | $ | 57,500 | | | $ | 13,179 | | | | — | | | $ | 24.45 | |
| 2021 | | $ | 57,500 | | | $ | 8,793 | | | | — | | | $ | 25.90 | |
| 2020 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2019 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2018 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2017 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2016 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| | | Total Amount | | | | | | | | | | | | | |
| | | Outstanding | | | | | | | Involuntary | | | Average | |
| | | Exclusive of | | | Asset | | | Liquidation | | | Market | |
| | | Treasury | | | Coverage | | | Preference | | | Value per | |
| Class and Year | | Securities(1) | | | per Unit(2) | | | per Unit(3) | | | Unit(4) | |
| | | (In thousands, except unit data) | |
| 2022 Notes | | | | | | | | | | | | | | | | |
| 2025 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2024 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2023 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2022 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2021 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2020 | | $ | 37,375 | | | $ | 10,708 | | | | — | | | $ | 24.60 | |
| 2019 | | $ | 37,375 | | | $ | 9,055 | | | | — | | | $ | 25.53 | |
| 2018 | | $ | 37,375 | | | $ | 7,014 | | | | — | | | $ | 25.52 | |
| 2017 | | $ | 37,375 | | | $ | 6,166 | | | | — | | | $ | 25.66 | |
| 2016 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2019 Notes | | | | | | | | | | | | | | | | |
| 2025 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2024 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2023 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2022 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2021 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2020 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2019 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2018 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2017 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2016 | | $ | 33,000 | | | $ | 7,127 | | | | — | | | $ | 25.42 | |
| 2022-1 Securitization | | | | | | | | | | | | | | | | |
| 2025 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2024 | | $ | 81,078 | | | $ | 9,969 | | | | — | | | | N/A | |
| 2023 | | $ | 100,000 | | | $ | 7,900 | | | | — | | | | N/A | |
| 2022 | | $ | 100,000 | | | $ | 7,578 | | | | — | | | | N/A | |
| 2021 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2020 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2019 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2018 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2017 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2016 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2019-1 Securitization | | | | | | | | | | | | | | | | |
| 2025 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2024 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2023 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2022 | | $ | 42,573 | | | $ | 17,799 | | | | — | | | | N/A | |
| 2021 | | $ | 70,500 | | | $ | 7,171 | | | | — | | | | N/A | |
| 2020 | | $ | 100,000 | | | $ | 4,002 | | | | — | | | | N/A | |
| 2019 | | $ | 100,000 | | | $ | 3,384 | | | | — | | | | N/A | |
| 2018 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2017 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| 2016 | | $ | — | | | $ | — | | | | — | | | | N/A | |
| Total senior securities | | | | | | | | | | | | | | | | |
| 2025 | | $ | 477,750 | | | $ | 1,667 | | | | — | | | | N/A | |
| 2024 | | $ | 472,078 | | | $ | 1,712 | | | | — | | | | N/A | |
| 2023 | | $ | 466,000 | | | $ | 1,695 | | | | — | | | | N/A | |
| 2022 | | $ | 439,323 | | | $ | 1,725 | | | | — | | | | N/A | |
| 2021 | | $ | 260,250 | | | $ | 1,943 | | | | — | | | | N/A | |
| 2020 | | $ | 187,625 | | | $ | 2,133 | | | | — | | | | N/A | |
| 2019 | | $ | 154,375 | | | $ | 2,192 | | | | — | | | | N/A | |
| 2018 | | $ | 127,875 | | | $ | 2,050 | | | | — | | | | N/A | |
| 2017 | | $ | 95,375 | | | $ | 2,416 | | | | — | | | | N/A | |
| 2016 | | $ | 96,000 | | | $ | 2,450 | | | | — | | | | N/A | |
|