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Reinsurance (Narrative) (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2025 | Jun. 30, 2024 | Jun. 30, 2025 | Jun. 30, 2024
Fronting |  |  |  |
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items] |  |  |  |
Gross losses and loss adjustment expenses | $ 1,300.0 | $ 593.9 | $ 2,300.0 | $ 1,200.0

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