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v3.25.3

Segment Reporting Disclosures (Narrative) (Details) $ in Thousands | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2025 USD ($) segment | Dec. 31, 2024 USD ($)
Segment Reporting Information [Line Items] |  |
Number of Reportable Segments | segment | 4 |
Markel Insurance |  |
Segment Reporting Information [Line Items] |  |
Goodwill, Impairment Loss | $ 0 |
Global Reinsurance Division [Member] |  |
Segment Reporting Information [Line Items] |  |
Gross premium volume |  | $ 1,200,000

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