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Goodwill And Intangible Assets (Components Of Goodwill) (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Goodwill [Line Items] |  |  |  |  |  |
Goodwill, beginning balance |  | $ 2,638,838 | [1] | $ 2,899,140 |  |
Acquisitions |  |  |  | 41,905 |  |
Dispositions |  |  |  | (132,455) |  |
Impairment of goodwill |  | 0 |  | (80,000) |  | $ 0
Adjustments to preliminary purchase price allocation |  | (16,752) |  | (83,358) |  |
Foreign currency movements and other adjustments |  | 2,663 |  | (6,394) |  |
Goodwill, ending balance |  | 2,624,749 | [1] | 2,638,838 | [1] | 2,899,140
Accumulated impairment losses | [1] | 190,600 |  | 190,600 |  |
Insurance [Member] |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Goodwill, beginning balance |  | 771,628 | [1] | 774,712 |  |
Acquisitions |  |  |  | 0 |  |
Dispositions |  |  |  | 0 |  |
Impairment of goodwill |  |  |  | 0 |  |
Adjustments to preliminary purchase price allocation |  | 0 |  | 0 |  |
Foreign currency movements and other adjustments |  | 1,195 |  | (3,084) |  |
Goodwill, ending balance |  | 772,823 | [1] | 771,628 | [1] | 774,712
Reinsurance [Member] |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Goodwill, beginning balance |  | 122,745 | [1] | 122,745 |  |
Acquisitions |  |  |  | 0 |  |
Dispositions |  |  |  | 0 |  |
Impairment of goodwill |  |  |  | 0 |  |
Adjustments to preliminary purchase price allocation |  | 0 |  | 0 |  |
Foreign currency movements and other adjustments |  | 0 |  | 0 |  |
Goodwill, ending balance |  | 122,745 | [1] | 122,745 | [1] | 122,745
Markel Ventures [Member] |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Goodwill, beginning balance |  | 1,153,909 | [1] | 1,196,590 |  |
Acquisitions |  |  |  | 41,905 |  |
Dispositions |  |  |  | 0 |  |
Impairment of goodwill |  |  |  | 0 |  |
Adjustments to preliminary purchase price allocation |  | (16,752) |  | (83,358) |  |
Foreign currency movements and other adjustments |  | 497 |  | (1,228) |  |
Goodwill, ending balance |  | 1,137,654 | [1] | 1,153,909 | [1] | 1,196,590
Accumulated impairment losses | [1] | 18,700 |  | 18,700 |  |
Other Operations [Member] |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Goodwill, beginning balance | [2] | 590,556 | [1] | 805,093 |  |
Acquisitions | [2] |  |  | 0 |  |
Dispositions | [2] |  |  | (132,455) |  |
Impairment of goodwill | [2] |  |  | (80,000) |  |
Adjustments to preliminary purchase price allocation | [2] | 0 |  | 0 |  |
Foreign currency movements and other adjustments | [2] | 971 |  | (2,082) |  |
Goodwill, ending balance | [2] | 591,527 | [1] | 590,556 | [1] | $ 805,093
Accumulated impairment losses | [1] | $ 171,900 |  | $ 171,900 |  |
[1] | As of December 31, 2023 and 2022, goodwill was net of accumulated impairment losses of $190.6 million, of which $171.9 million was in Other and $18.7 million was in Markel Ventures.
[2] | Amounts included in Other 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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