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Securities, at Fair Value - Impairment and Other Net Gain/(Loss) on Securities and Other Portfolio Investments (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Gain (Loss) on Securities [Line Items] |  |  |  |
Total Impairment and other net gain/(loss) on securities and other portfolio investments | $ 18,004 | $ 22,928 | $ 45,828 | $ 15,310
Securities |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Net unrealized gain/(loss) on other portfolio investments | 17,798 | 16,890 | 42,006 | 9,591
Net realized gain/(loss) on other portfolio investments | 668 | 7,324 | 902 | 9,992
Impairment of securities | 0 | 0 | 0 | 0
Total Impairment and other net gain/(loss) on securities and other portfolio investments | 18,466 | 24,214 | 42,908 | 19,583
Other Portfolio Investments |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Net unrealized gain/(loss) on other portfolio investments | (488) | (1,286) | 2,901 | (4,273)
Net realized gain/(loss) on other portfolio investments | $ 26 | $ 0 | $ 19 | $ 0

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