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Reinsurance (Effect Of Reinsurance And Retrocessional Reinsurance On Losses) (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Effects of Reinsurance [Line Items] |  |  |  |
Net losses and loss adjustment expenses | $ 1,253,826 | $ 1,290,612 | $ 3,796,525 | $ 3,810,934
Underwriting [Member] |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |
Gross losses and loss adjustment expenses | 1,566,985 | 1,710,637 | 4,900,250 | 4,982,304
Ceded losses and loss adjustment expenses | (313,061) | (419,194) | (1,103,552) | (1,170,585)
Net losses and loss adjustment expenses | $ 1,253,924 | $ 1,291,443 | $ 3,796,698 | $ 3,811,719

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