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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, 2024 | Jun. 30, 2023 | Jun. 30, 2024 | Jun. 30, 2023
Investment Company, Nonconsolidated Subsidiary [Line Items] |  |  |  |
Total investment income | $ 94,588 | $ 95,492 | $ 185,144 | $ 187,445
Interest and other financing expenses | 33,113 | 31,700 | 64,129 | 62,496
Total expenses | 56,776 | 55,728 | 110,678 | 110,260
Net investment income | 38,673 | 40,860 | 76,228 | 79,344
Net realized (losses) gains on investments |  |  | (42,993) | 3,231
Net change in unrealized (depreciation) appreciation of investments |  |  | 33,529 | (1,461)
SLP III |  |  |  |
Investment Company, Nonconsolidated Subsidiary [Line Items] |  |  |  |
Interest income | 16,596 | 16,149 | 33,385 | 31,235
Other income | 58 | 66 | 85 | 157
Total investment income | 16,654 | 16,215 | 33,470 | 31,392
Interest and other financing expenses | 8,921 | 8,869 | 17,711 | 17,275
Other expenses | 267 | 293 | 508 | 536
Total expenses | 9,188 | 9,162 | 18,219 | 17,811
Net investment income | 7,466 | 7,053 | 15,251 | 13,581
Net realized (losses) gains on investments | (238) | 12 | (5,907) | (1,855)
Net change in unrealized (depreciation) appreciation of investments | (4,225) | 6,915 | 6,498 | 15,954
Net increase in members' capital | 3,003 | 13,980 | 15,842 | 27,680
SLP IV |  |  |  |
Investment Company, Nonconsolidated Subsidiary [Line Items] |  |  |  |
Interest income | 12,157 | 11,991 | 24,119 | 23,249
Other income | 46 | 42 | 67 | 158
Total investment income | 12,203 | 12,033 | 24,186 | 23,407
Interest and other financing expenses | 6,642 | 6,176 | 12,742 | 12,008
Other expenses | 225 | 227 | 449 | 432
Total expenses | 6,867 | 6,403 | 13,191 | 12,440
Net investment income | 5,336 | 5,630 | 10,995 | 10,967
Net realized (losses) gains on investments | (176) | 15 | (4,874) | (1,654)
Net change in unrealized (depreciation) appreciation of investments | (3,384) | 4,160 | 3,544 | 9,638
Net increase in members' capital | $ 1,776 | $ 9,805 | $ 9,665 | $ 18,951

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