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Investments - Selected Statement of Operations Information for SLP III and SLP IV (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Investment Company, Nonconsolidated Subsidiary [Line Items] |  |  |  |
Total investment income | $ 80,529 | $ 95,327 | $ 249,682 | $ 280,471
Interest and other financing expenses | 31,720 | 37,661 | 94,232 | 101,790
Total expenses | 51,002 | 60,791 | 155,348 | 171,469
Net investment income | 34,071 | 35,506 | 103,286 | 111,734
Net realized (losses) gains on investments |  |  | 51,223 | (43,524)
Net change in unrealized (depreciation) appreciation of investments |  |  | (111,171) | 23,368
SLP III |  |  |  |
Investment Company, Nonconsolidated Subsidiary [Line Items] |  |  |  |
Interest income | 16,172 | 17,860 | 46,239 | 51,245
Other income | 64 | 49 | 253 | 134
Total investment income | 16,236 | 17,909 | 46,492 | 51,379
Interest and other financing expenses | 8,227 | 8,888 | 24,444 | 26,599
Other expenses | 329 | 229 | 932 | 737
Total expenses | 8,556 | 9,117 | 25,376 | 27,336
Net investment income | 7,680 | 8,792 | 21,116 | 24,043
Net realized (losses) gains on investments | (1,294) | 74 | (829) | (5,833)
Net change in unrealized (depreciation) appreciation of investments | (1,122) | (1,493) | (9,439) | 5,005
Net increase in members' capital | 5,264 | 7,373 | 10,848 | 23,215
SLP IV |  |  |  |
Investment Company, Nonconsolidated Subsidiary [Line Items] |  |  |  |
Interest income | 11,308 | 12,906 | 31,291 | 37,025
Other income | 65 | 10 | 156 | 77
Total investment income | 11,373 | 12,916 | 31,447 | 37,102
Interest and other financing expenses | 5,986 | 6,694 | 16,171 | 19,436
Other expenses | 258 | 202 | 673 | 651
Total expenses | 6,244 | 6,896 | 16,844 | 20,087
Net investment income | 5,129 | 6,020 | 14,603 | 17,015
Net realized (losses) gains on investments | (541) | 133 | (681) | (4,741)
Net change in unrealized (depreciation) appreciation of investments | (1,569) | (2,076) | (6,675) | 1,468
Net increase in members' capital | $ 3,019 | $ 4,077 | $ 7,247 | $ 13,742

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