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Goodwill And Intangible Assets Goodwill And Intangible Assets (Components of Net Intangible Assets) (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Intangible [Line Items] |  |  |  |
Net intangible assets, beginning balance |  | $ 1,588,684 | $ 1,747,464 |
Intangible Assets Acquired During Period |  | 52,909 |  |
Dispositions |  |  | (2,000) |
Amortization of intangible assets |  | (181,472) | (180,614) | $ (178,778)
Adjustments to preliminary purchase price allocation |  |  | 22,671 |
Foreign currency movements and other adjustments |  | (501) | 1,163 |
Net intangible assets, ending balance |  | 1,459,620 | 1,588,684 | 1,747,464
Underwriting [Member] |  |  |  |
Intangible [Line Items] |  |  |  |
Net intangible assets, beginning balance | [1] | 325,344 | 362,322 |
Intangible Assets Acquired During Period | [1] | 0 |  |
Dispositions |  |  | 0 |
Amortization of intangible assets | [1] | 37,276 | 37,076 |
Adjustments to preliminary purchase price allocation |  |  | 0 |
Foreign currency movements and other adjustments | [1] | (117) | 98 |
Net intangible assets, ending balance | [1] | 287,951 | 325,344 | 362,322
Markel Ventures [Member] |  |  |  |
Intangible [Line Items] |  |  |  |
Net intangible assets, beginning balance |  | 736,717 | 796,297 |
Intangible Assets Acquired During Period |  | 52,909 |  |
Dispositions |  |  | 0 |
Amortization of intangible assets |  | (81,317) | (82,370) |
Adjustments to preliminary purchase price allocation |  |  | 22,671 |
Foreign currency movements and other adjustments |  | 154 | 119 |
Net intangible assets, ending balance |  | 708,463 | 736,717 | 796,297
Other Insurance Operations |  |  |  |
Intangible [Line Items] |  |  |  |
Net intangible assets, beginning balance | [2] | 526,623 | 588,845 |
Intangible Assets Acquired During Period | [2] | 0 |  |
Dispositions |  |  | (2,000) |
Amortization of intangible assets | [2] | (62,879) | (61,168) |
Adjustments to preliminary purchase price allocation |  |  | 0 |
Foreign currency movements and other adjustments | [2] | (538) | 946 |
Net intangible assets, ending balance | [2] | $ 463,206 | $ 526,623 | $ 588,845
[1] | Amounts included in Underwriting reflect the intangible assets associated with the Company's underwriting segments, which are not allocated between the Insurance and Reinsurance segments.
[2] | Amounts included in other insurance operations reflect the Company's operations that are not included in a reportable segment and are primarily related to the Company's program services and insurance-linked securities operations.

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