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Segment Reporting Disclosures (Summary of Additional Measures for Markel Ventures) (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Segment Reporting Information [Line Items] |  |  |  |
Interest expense |  | $ 185,077 | $ 196,062 | $ 183,579
Income tax (expense) benefit |  | 552,616 | (48,209) | 683,961
Markel Ventures [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Depreciation |  | 108,605 | 102,055 | 72,580
Interest expense | [1] | 47,227 | 46,780 | 35,031
Income tax (expense) benefit |  | 85,295 | 61,588 | 43,626
Capital expenditure |  | 221,036 | 225,230 | 124,451
Intercompany interest expense | [1] | $ 26,500 | $ 27,400 | $ 25,800
[1] | Interest expense for the years ended December 31, 2023, 2022 and 2021 included intercompany interest expense of $26.5 million, $27.4 million and $25.8 million, respectively, which was eliminated in consolidation.

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