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Reinsurance (Effect Of Reinsurance And Retrocessional Reinsurance On Losses) (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
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Jun. 30, 2025 | Jun. 30, 2024 | Jun. 30, 2025 | Jun. 30, 2024
Effects of Reinsurance [Line Items] |  |  |  |
Net losses and loss adjustment expenses | $ 1,288,034 | $ 1,232,575 | $ 2,542,699 | $ 2,520,322
Underwriting [Member] |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |
Gross losses and loss adjustment expenses | 1,659,756 | 1,577,820 | 3,333,265 | 3,271,667
Ceded losses and loss adjustment expenses | (371,564) | (345,224) | (790,491) | (751,391)
Net losses and loss adjustment expenses | $ 1,288,192 | $ 1,232,596 | $ 2,542,774 | $ 2,520,276

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