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Investments - Selected Statement of Operations Information for SLP III and SLP IV (Details) - USD ($) $ in Thousands | 8 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2021 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Investment Company, Nonconsolidated Subsidiary [Line Items] |  |  |  |
Total investment income |  | $ 374,836 | $ 294,630 | $ 270,959
Interest and other financing expenses |  | 124,784 | 92,421 | 73,098
Total expenses |  | 218,637 | 178,841 | 165,349
Net investment income before income taxes |  | 160,316 | 120,429 | 118,958
Net realized (losses) gains on investments |  | (32,854) | 52,703 | (3,864)
Net change in unrealized (depreciation) appreciation of investments |  | 10,316 | (84,134) | 92,386
SLP III |  |  |  |
Investment Company, Nonconsolidated Subsidiary [Line Items] |  |  |  |
Interest income |  | 64,921 | 41,382 | 31,240
Other income |  | 502 | 774 | 573
Total investment income |  | 65,423 | 42,156 | 31,813
Interest and other financing expenses |  | 35,336 | 19,274 | 10,624
Other expenses |  | 1,143 | 863 | 804
Total expenses |  | 36,479 | 20,137 | 11,428
Net investment income before income taxes |  | 28,944 | 22,019 | 20,385
Net realized (losses) gains on investments |  | (2,663) | (247) | 572
Net change in unrealized (depreciation) appreciation of investments |  | 32,206 | (42,366) | 6,360
Net (decrease) increase in members' capital |  | 58,487 | (20,594) | $ 27,317
SLP IV |  |  |  |
Investment Company, Nonconsolidated Subsidiary [Line Items] |  |  |  |
Interest income | $ 14,821 | 48,082 | 31,017 |
Other income | 234 | 498 | 561 |
Total investment income | 15,055 | 48,580 | 31,578 |
Interest and other financing expenses | 4,163 | 24,860 | 13,580 |
Other expenses | 773 | 958 | 757 |
Total expenses | 4,936 | 25,818 | 14,337 |
Net investment income before income taxes | 10,119 | 22,762 | 17,241 |
Net realized (losses) gains on investments | 183 | (1,857) | (164) |
Net change in unrealized (depreciation) appreciation of investments | 5,033 | 22,982 | (31,018) |
Net (decrease) increase in members' capital | $ 15,335 | $ 43,887 | $ (13,941) |

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