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Segment Reporting Disclosures (Company's Segment Disclosures) (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2023 | Jun. 30, 2022 | Jun. 30, 2023 | Jun. 30, 2022
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |
Gross premium volume |  | $ 3,788,185 |  | $ 3,280,049 |  | $ 7,224,197 |  | $ 6,678,336 |
Net written premiums |  | 2,207,693 |  | 2,099,795 |  | 4,425,471 |  | 4,264,529 |
Earned premiums |  | 2,031,143 |  | 1,833,104 |  | 3,998,847 |  | 3,592,874 |
Losses and loss adjustment expenses, current accident year |  | (1,255,767) |  | (1,085,215) |  | (2,500,098) |  | (2,153,910) |
Losses and loss adjustment expenses, prior accident year |  | 67,891 |  | 26,405 |  | 139,208 |  | 122,728 |
Amortization of policy acquisition costs |  | (438,719) |  | (392,983) |  | (860,851) |  | (775,143) |
Other underwriting expenses |  | (259,168) |  | (216,486) |  | (512,741) |  | (424,691) |
Underwriting profit (loss) |  | 145,380 |  | 164,825 |  | 264,365 |  | 361,858 |
Net investment income |  | 169,693 |  | 96,795 |  | 329,028 |  | 189,099 |
Net investment gains (losses) |  | 484,527 |  | (1,554,643) |  | 857,090 |  | (1,913,042) |
Products revenues |  | 784,882 |  | 776,959 |  | 1,362,808 |  | 1,258,580 |
Services and other revenues |  | 672,291 |  | 639,992 |  | 1,238,152 |  | 1,270,932 |
Products expenses |  | (651,469) |  | (697,718) |  | (1,167,225) |  | (1,145,537) |
Services and other expenses |  | (590,817) |  | (557,481) |  | (1,071,436) |  | (1,147,372) |
Amortization of intangible assets |  | (44,423) | [1] | (45,523) | [2] | (88,822) | [3] | (91,572) | [4]
Segment profit (loss) |  | 970,064 |  | (1,176,794) |  | 1,723,960 |  | (1,217,054) |
Interest expense |  | (47,221) |  | (50,050) |  | (96,659) |  | (99,742) |
Net foreign exchange gains (losses) |  | (14,976) |  | 105,067 |  | (47,904) |  | 128,071 |
Income (Loss) before income taxes |  | 907,867 |  | (1,121,777) |  | 1,579,397 |  | (1,188,725) |
Insurance [Member] |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |
Gross premium volume |  | 2,455,403 |  | 2,237,158 |  | 4,553,341 |  | 4,180,464 |
Net written premiums |  | 1,946,528 |  | 1,828,162 |  | 3,648,669 |  | 3,439,182 |
Earned premiums |  | 1,763,186 |  | 1,570,001 |  | 3,474,110 |  | 3,047,149 |
Losses and loss adjustment expenses, current accident year |  | (1,079,450) |  | (919,283) |  | (2,156,996) |  | (1,805,520) |
Losses and loss adjustment expenses, prior accident year |  | 61,562 |  | 43,693 |  | 124,190 |  | 142,333 |
Amortization of policy acquisition costs |  | (367,145) |  | (323,826) |  | (727,499) |  | (634,232) |
Other underwriting expenses |  | (243,502) |  | (204,171) |  | (482,650) |  | (395,822) |
Underwriting profit (loss) |  | 134,651 |  | 166,414 |  | 231,155 |  | 353,908 |
Net investment income |  | 0 |  | 0 |  | 0 |  | 0 |
Net investment gains (losses) |  | 0 |  | 0 |  | 0 |  | 0 |
Products revenues |  | 0 |  | 0 |  | 0 |  | 0 |
Services and other revenues |  | 0 |  | 0 |  | 0 |  | 0 |
Products expenses |  | 0 |  | 0 |  | 0 |  | 0 |
Services and other expenses |  | 0 |  | 0 |  | 0 |  | 0 |
Amortization of intangible assets |  | 0 | [1] | 0 | [2] | 0 | [3] | 0 | [4]
Segment profit (loss) |  | 134,651 |  | 166,414 |  | 231,155 |  | 353,908 |
Reinsurance [Member] |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |
Gross premium volume |  | 281,100 |  | 289,056 |  | 833,161 |  | 865,372 |
Net written premiums |  | 261,496 |  | 273,838 |  | 777,587 |  | 829,058 |
Earned premiums |  | 268,288 |  | 264,154 |  | 525,522 |  | 548,121 |
Losses and loss adjustment expenses, current accident year |  | (176,317) |  | (165,932) |  | (343,102) |  | (348,390) |
Losses and loss adjustment expenses, prior accident year |  | 7,974 |  | (13,577) |  | 16,678 |  | (15,660) |
Amortization of policy acquisition costs |  | (71,574) |  | (69,125) |  | (133,352) |  | (140,879) |
Other underwriting expenses |  | (13,187) |  | (11,681) |  | (26,328) |  | (26,070) |
Underwriting profit (loss) |  | 15,184 |  | 3,839 |  | 39,418 |  | 17,122 |
Net investment income |  | 0 |  | 0 |  | 0 |  | 0 |
Net investment gains (losses) |  | 0 |  | 0 |  | 0 |  | 0 |
Products revenues |  | 0 |  | 0 |  | 0 |  | 0 |
Services and other revenues |  | 0 |  | 0 |  | 0 |  | 0 |
Products expenses |  | 0 |  | 0 |  | 0 |  | 0 |
Services and other expenses |  | 0 |  | 0 |  | 0 |  | 0 |
Amortization of intangible assets |  | 0 | [1] | 0 | [2] | 0 | [3] | 0 | [4]
Segment profit (loss) |  | 15,184 |  | 3,839 |  | 39,418 |  | 17,122 |
Investing [Member] |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |
Gross premium volume |  | 0 |  | 0 |  | 0 |  | 0 |
Net written premiums |  | 0 |  | 0 |  | 0 |  | 0 |
Earned premiums |  | 0 |  | 0 |  | 0 |  | 0 |
Losses and loss adjustment expenses, current accident year |  | 0 |  | 0 |  | 0 |  | 0 |
Losses and loss adjustment expenses, prior accident year |  | 0 |  | 0 |  | 0 |  | 0 |
Amortization of policy acquisition costs |  | 0 |  | 0 |  | 0 |  | 0 |
Other underwriting expenses |  | 0 |  | 0 |  | 0 |  | 0 |
Underwriting profit (loss) |  | 0 |  | 0 |  | 0 |  | 0 |
Net investment income |  | 168,927 |  | 96,695 |  | 327,521 |  | 188,992 |
Net investment gains (losses) |  | 484,527 |  | (1,554,643) |  | 857,090 |  | (1,913,042) |
Products revenues |  | 0 |  | 0 |  | 0 |  | 0 |
Services and other revenues |  | (6,378) |  | (3,137) |  | (8,758) |  | (22,707) |
Products expenses |  | 0 |  | 0 |  | 0 |  | 0 |
Services and other expenses |  | 0 |  | 0 |  | 0 |  | 0 |
Amortization of intangible assets |  | 0 | [1] | 0 | [2] | 0 | [3] | 0 | [4]
Segment profit (loss) |  | 647,076 |  | (1,461,085) |  | 1,175,853 |  | (1,746,757) |
Markel Ventures [Member] |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |
Gross premium volume |  | 0 |  | 0 |  | 0 |  | 0 |
Net written premiums |  | 0 |  | 0 |  | 0 |  | 0 |
Earned premiums |  | 0 |  | 0 |  | 0 |  | 0 |
Losses and loss adjustment expenses, current accident year |  | 0 |  | 0 |  | 0 |  | 0 |
Losses and loss adjustment expenses, prior accident year |  | 0 |  | 0 |  | 0 |  | 0 |
Amortization of policy acquisition costs |  | 0 |  | 0 |  | 0 |  | 0 |
Other underwriting expenses |  | 0 |  | 0 |  | 0 |  | 0 |
Underwriting profit (loss) |  | 0 |  | 0 |  | 0 |  | 0 |
Net investment income |  | 766 |  | 100 |  | 1,507 |  | 107 |
Net investment gains (losses) |  | 0 |  | 0 |  | 0 |  | 0 |
Products revenues |  | 784,882 |  | 776,959 |  | 1,362,808 |  | 1,258,580 |
Services and other revenues |  | 600,931 |  | 584,339 |  | 1,126,944 |  | 1,053,103 |
Products expenses |  | (651,469) |  | (697,718) |  | (1,167,225) |  | (1,145,537) |
Services and other expenses |  | (565,060) |  | (536,057) |  | (1,061,806) |  | (967,960) |
Amortization of intangible assets |  | (19,859) | [1] | (20,577) | [2] | (39,410) | [3] | (41,510) | [4]
Segment profit (loss) |  | 150,191 |  | 107,046 |  | 222,818 |  | 156,783 |
Interest expense | [5] | (12,899) |  | (11,025) |  | (25,822) |  | (22,203) |
Other [Member] |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |
Gross premium volume |  | 1,051,682 | [6] | 753,835 | [7] | 1,837,695 | [8] | 1,632,500 | [9]
Net written premiums |  | (331) | [6] | (2,205) | [7] | (785) | [8] | (3,711) | [9]
Earned premiums |  | (331) | [6] | (1,051) | [7] | (785) | [8] | (2,396) | [9]
Losses and loss adjustment expenses, current accident year |  | 0 | [6] | 0 | [7] | 0 | [8] | 0 | [9]
Losses and loss adjustment expenses, prior accident year |  | (1,645) | [6] | (3,711) | [7] | (1,660) | [8] | (3,945) | [9]
Amortization of policy acquisition costs |  | 0 | [6] | (32) | [7] | 0 | [8] | (32) | [9]
Other underwriting expenses |  | (2,479) | [6] | (634) | [7] | (3,763) | [8] | (2,799) | [9]
Underwriting profit (loss) |  | (4,455) | [6] | (5,428) | [7] | (6,208) | [8] | (9,172) | [9]
Net investment income |  | 0 | [6] | 0 | [7] | 0 | [8] | 0 | [9]
Net investment gains (losses) |  | 0 | [6] | 0 | [7] | 0 | [8] | 0 | [9]
Products revenues |  | 0 | [6] | 0 | [7] | 0 | [8] | 0 | [9]
Services and other revenues |  | 77,738 | [6] | 58,790 | [7] | 119,966 | [8] | 240,536 | [9]
Products expenses |  | 0 | [6] | 0 | [7] | 0 | [8] | 0 | [9]
Services and other expenses |  | (25,757) | [6] | (21,424) | [7] | (9,630) | [8] | (179,412) | [9]
Amortization of intangible assets |  | (24,564) | [1],[6] | (24,946) | [2],[7] | (49,412) | [3],[8] | (50,062) | [4],[9]
Segment profit (loss) |  | 22,962 | [6] | 6,992 | [7] | 54,716 | [8] | 1,890 | [9]
Underwriting Segments [Member] |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |
Amortization of intangible assets |  | $ 9,300 |  | $ 9,600 | [2] | $ 18,800 | [3] | $ 19,400 | [4]
[1] | Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets attributable to the Company's underwriting segments, included in Other, was $9.3 million for the quarter ended June 30, 2023
[2] | Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets attributable to the Company's underwriting segments, included in Other, was $9.6 million for the quarter ended June 30, 2022
[3] | Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets attributable to the Company's underwriting segments, included in Other, was $18.8 million for the six months ended June 30, 2023.
[4] | Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets attributable to the Company's underwriting segments, included in Other, was $19.4 million for the six months ended June 30, 2022.
[5] | Interest expense for the quarter and six months ended June 30, 2023 included intercompany interest expense of $6.6 million and $13.3 million, respectively. Interest expense for the quarter and six months ended June 30, 2022 included intercompany interest expense of $7.0 million and $14.1 million. Intercompany interest expense was eliminated in consolidation.
[6] | Other represents the total profit (loss) attributable to the Company's operations that are not included in a reportable segment, as well as amortization of intangible assets attributable to underwriting segments, which is not allocated between the Insurance and Reinsurance segments.
[7] | Other represents the total profit (loss) attributable to the Company's operations that are not included in a reportable segment, as well as amortization of intangible assets attributable to underwriting segments, which is not allocated between the Insurance and Reinsurance segments.
[8] | Other represents the total profit (loss) attributable to the Company's operations that are not included in a reportable segment, as well as amortization of intangible assets attributable to underwriting segments, which is not allocated between the Insurance and Reinsurance segments.
[9] | Other represents the total profit (loss) attributable to the Company's operations that are not included in a reportable segment, as well as amortization of intangible assets attributable to underwriting segments, which is not allocated between the Insurance and Reinsurance segments.

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