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Variable Interest Entities (Narrative) (Details) - USD ($) $ in Thousands | 1 Months Ended | 3 Months Ended | 6 Months Ended |  |
--- | --- | --- | --- | --- | ---
Jun. 30, 2022 | Jun. 30, 2023 | Jun. 30, 2022 | Jun. 30, 2023 | Jun. 30, 2022 | Dec. 31, 2022 | Mar. 31, 2022
Variable Interest Entity [Line Items] |  |  |  |  |  |  |
Cash funding used to purchase Markel CATCo Funds' interests in Markel CATCo Re |  |  |  |  |  |  | $ 45,100
Additional payments made, net of insurance in proceeds, to Markel CATCo Funds investors |  |  |  |  |  |  | $ 101,900
Returned capital from Markel CATCo Re | $ 24,900 |  |  |  |  |  |
Investment in Markel CATCo Re |  | $ 20,100 |  | $ 20,100 |  | $ 20,100 |
Percentage of Markel CATCo Re net equity held by the Company |  | 25.00% |  | 25.00% |  | 23.00% |
Tail risk cover in Markel CATCo transaction |  | $ 142,700 |  | $ 142,700 |  |  |
Favorable development on prior years' loss reserves |  |  |  | 139,208 | $ 122,728 |  |
Redemption of Markel CATCo Re noncontrolling interests |  |  |  | (88,997) | 0 |  |
Noncontrolling Interests [Member] |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |
Redemption of Markel CATCo Re noncontrolling interests |  |  | $ (22,261) | (62,646) | (22,261) |  |
Markel CATCo Re |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |
Favorable development on prior years' loss reserves |  | $ (8,700) | $ (28,200) | $ (53,500) | $ (28,200) |  |

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- Definition This amount is the Company's preference shares investment in Markel CATCo Re. + References No definition available. + Details
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- Definition Percentage of Markel CATCo Re net equity held by the Company + References No definition available. + Details
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