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Net Investment Income (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2023 | Sep. 30, 2022
Net Investment Income [Line Items] |  |  |  |
Gross investment income | $ 272,781 | $ 205,143 | $ 745,705 | $ 554,252
Investment expense | (1,837) | (2,327) | (6,211) | (6,350)
Net investment income | 270,944 | 202,816 | 739,494 | 547,902
Fixed maturity securities, including cash and cash equivalents and loans receivable |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Gross investment income | 239,727 | 146,051 | 653,200 | 371,724
Arbitrage trading account (1) |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Gross investment income | 4,450 | 36,045 | 5,444 | 121,919
Equity securities |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Gross investment income | 12,714 | 14,650 | 41,714 | 38,303
Investment funds |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Gross investment income | 17,876 | 10,694 | 53,168 | 24,008
Real estate |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Gross investment income | $ (1,986) | $ (2,297) | $ (7,821) | $ (1,702)

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