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Products, Services and Other Revenues (Schedule Of Revenues From Contracts With Customers By Type) (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023
Disaggregation of Revenue [Line Items] |  |  |  |
Leasing revenues | $ 45,726 | $ 50,994 | $ 123,514 | $ 130,051
Program services and other fronting fees | 47,613 | 39,499 | 129,861 | 105,952
Equity method and other investments income (loss) | 8,677 | (5,054) | 45,466 | (12,704)
Disposition gain |  |  | 0 | 16,923
Other revenues (losses) | 1,501 | 13,438 | 3,987 | 31,127
Products Revenues and Services and Other Revenues | 1,348,149 | 1,327,151 | 4,098,327 | 3,928,111
Markel Ventures [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Leasing revenues | 45,726 | 50,994 | 123,514 | 130,051
Program services and other fronting fees | 0 | 0 | 0 | 0
Equity method and other investments income (loss) | (6,294) | (21) | 292 | 1,087
Disposition gain |  |  | 0 | 0
Other revenues (losses) | 1,563 | 13,438 | 4,067 | 31,079
Products Revenues and Services and Other Revenues | 1,257,528 | 1,245,577 | 3,848,243 | 3,735,329
Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Leasing revenues | 0 | 0 | 0 | 0
Program services and other fronting fees | 47,613 | 39,499 | 129,861 | 105,952
Equity method and other investments income (loss) | 14,971 | (5,033) | 45,174 | (13,791)
Disposition gain |  |  | 0 | 16,923
Other revenues (losses) | (62) | 0 | (80) | 48
Products Revenues and Services and Other Revenues | 90,621 | 81,574 | 250,084 | 192,782
Revenue from contracts with customers [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Other revenues | 1,244,632 | 1,228,274 | 3,795,499 | 3,656,762
Revenue from contracts with customers [Member] | Products [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Other revenues | 605,471 | 585,707 | 2,040,699 | 1,921,773
Revenue from contracts with customers [Member] | Services [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Other revenues | 613,303 | 598,363 | 1,686,460 | 1,658,881
Revenue from contracts with customers [Member] | Management Fees [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Other revenues | 25,858 | 44,204 | 68,340 | 76,108
Revenue from contracts with customers [Member] | Markel Ventures [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Other revenues | 1,216,533 | 1,181,166 | 3,720,370 | 3,573,112
Revenue from contracts with customers [Member] | Markel Ventures [Member] | Products [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Other revenues | 605,471 | 585,707 | 2,040,699 | 1,921,773
Revenue from contracts with customers [Member] | Markel Ventures [Member] | Services [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Other revenues | 611,062 | 595,459 | 1,679,671 | 1,651,339
Revenue from contracts with customers [Member] | Markel Ventures [Member] | Management Fees [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Other revenues | 0 | 0 | 0 | 0
Revenue from contracts with customers [Member] | Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Other revenues | 28,099 | 47,108 | 75,129 | 83,650
Revenue from contracts with customers [Member] | Other [Member] | Products [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Other revenues | 0 | 0 | 0 | 0
Revenue from contracts with customers [Member] | Other [Member] | Services [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Other revenues | 2,241 | 2,904 | 6,789 | 7,542
Revenue from contracts with customers [Member] | Other [Member] | Management Fees [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Other revenues | $ 25,858 | $ 44,204 | $ 68,340 | $ 76,108

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