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Segment Reporting Disclosures (Narrative) (Details) - United States [Member] | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Underwriting Operations [Member] |  |  |
Revenue, Major Customer [Line Items] |  |  |
Percentage of gross premiums written | 80.00% | 80.00% | 80.00%
Markel Ventures [Member] |  |  |
Revenue, Major Customer [Line Items] |  |  |
Percentage of revenue attributable to U.S. | 95.00% | 96.00% | 95.00%

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Details
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X
- Details
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X
- Details
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