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Investments - Selected Statement of Operations Information for SLP III and SLP IV (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2025 | Jun. 30, 2024 | Jun. 30, 2025 | Jun. 30, 2024
Investment Company, Nonconsolidated Subsidiary [Line Items] |  |  |  |
Total investment income | $ 83,490 | $ 94,588 | $ 169,153 | $ 185,144
Interest and other financing expenses | 31,138 | 33,113 | 62,512 | 64,129
Total expenses | 51,483 | 56,776 | 104,346 | 110,678
Net investment income | 34,593 | 38,673 | 69,215 | 76,228
Net realized gains (losses) on investments |  |  | 51,214 | (42,993)
Net change in unrealized (depreciation) appreciation of investments |  |  | (89,607) | 33,529
SLP III |  |  |  |
Investment Company, Nonconsolidated Subsidiary [Line Items] |  |  |  |
Interest income | 14,936 | 16,596 | 30,067 | 33,385
Other income | 113 | 58 | 189 | 85
Total investment income | 15,049 | 16,654 | 30,256 | 33,470
Interest and other financing expenses | 8,037 | 8,921 | 16,217 | 17,711
Other expenses | 297 | 267 | 603 | 508
Total expenses | 8,334 | 9,188 | 16,820 | 18,219
Net investment income | 6,715 | 7,466 | 13,436 | 15,251
Net realized gains (losses) on investments | 144 | (238) | 465 | (5,907)
Net change in unrealized (depreciation) appreciation of investments | (170) | (4,225) | (8,317) | 6,498
Net increase in members' capital | 6,689 | 3,003 | 5,584 | 15,842
SLP IV |  |  |  |
Investment Company, Nonconsolidated Subsidiary [Line Items] |  |  |  |
Interest income | 9,906 | 12,157 | 19,983 | 24,119
Other income | 61 | 46 | 91 | 67
Total investment income | 9,967 | 12,203 | 20,074 | 24,186
Interest and other financing expenses | 5,053 | 6,642 | 10,185 | 12,742
Other expenses | 193 | 225 | 415 | 449
Total expenses | 5,246 | 6,867 | 10,600 | 13,191
Net investment income | 4,721 | 5,336 | 9,474 | 10,995
Net realized gains (losses) on investments | 89 | (176) | (140) | (4,874)
Net change in unrealized (depreciation) appreciation of investments | (1,343) | (3,384) | (5,106) | 3,544
Net increase in members' capital | $ 3,467 | $ 1,776 | $ 4,228 | $ 9,665

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