v3.26.1
Segment Reporting Disclosures (Company's Segment Disclosures) (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Segment Reporting [Line Items]        
Earned premiums $ 2,071,778 $ 2,141,691 $ 4,120,664 $ 4,231,065
Net investment income 256,123 230,009 512,013 467,104
Products revenues 859,465 846,925 1,431,886 1,408,049
Services and other revenues 831,071 803,918 1,504,479 1,464,501
Operating revenues 4,018,437 4,022,543 7,569,042 7,570,719
Attritional Current Year Claims and Claims Adjustment Expense (1,312,526) (1,371,953) (2,548,378) (2,710,661)
Catastrophe Current Year Claims and Claims Adjustment Expense (40,983) [1] 5,187 (76,011) [1] (60,877)
Losses and loss adjustment expenses, prior accident year 166,358 78,732 270,421 228,839
Amortization of policy acquisition costs (420,576) (435,365) (833,506) (852,387)
Other underwriting expenses (315,235) (338,846) (642,133) (669,262)
Products expenses (723,458) (707,381) (1,240,888) (1,207,289)
Services and other expenses (935,896) (674,587) (1,564,680) (1,242,215)
Adjusted operating income (loss) 436,121 578,330 933,867 1,056,867
Net investment gains (losses) 1,167,525 580,223 439,963 431,152
Amortization of acquired intangible assets (43,301) (51,213) (86,814) (98,155)
Interest expense (52,390) (53,076) (103,276) (105,216)
Net foreign exchange gains (losses) 10,378 (191,909) 64,655 (264,542)
Income Before Income Taxes 1,518,333 862,355 1,248,395 1,020,106
Markel Insurance        
Segment Reporting [Line Items]        
Earned premiums 1,992,361 2,063,622 3,961,700 4,080,161
Net investment income 231,223 207,728 460,842 415,245
Products revenues 0 0 0 0
Services and other revenues 10,330 8,283 13,057 10,903
Operating revenues 2,233,914 2,279,633 4,435,599 4,506,309
Attritional Current Year Claims and Claims Adjustment Expense (1,263,694) (1,335,801) (2,449,604) (2,631,324)
Catastrophe Current Year Claims and Claims Adjustment Expense (40,983) [1] 5,187 (76,011) [1] (60,877)
Losses and loss adjustment expenses, prior accident year 166,560 78,934 273,499 227,771
Amortization of policy acquisition costs (414,342) (429,109) (821,071) (840,385)
Other underwriting expenses (297,783) (319,633) (604,145) (631,984)
Products expenses 0 0 0 0
Services and other expenses (7,182) (9,456) (12,287) (17,640)
Adjusted operating income (loss) 376,490 269,755 745,980 551,870
Net investment gains (losses) 1,030,284 580,572 476,370 356,378
Industrial        
Segment Reporting [Line Items]        
Earned premiums 0 0 0 0
Net investment income 0 0 0 0
Products revenues 421,895 424,573 819,620 793,818
Services and other revenues 616,173 591,142 1,101,506 1,051,471
Operating revenues 1,038,068 1,015,715 1,921,126 1,845,289
Attritional Current Year Claims and Claims Adjustment Expense 0 0 0 0
Catastrophe Current Year Claims and Claims Adjustment Expense 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
Products expenses (381,181) (366,283) (741,131) (692,318)
Services and other expenses (581,453) (545,919) (1,055,275) (990,694)
Adjusted operating income (loss) 75,434 103,513 124,720 162,277
Net investment gains (losses) 0 0 0 0
Financial        
Segment Reporting [Line Items]        
Earned premiums 79,417 78,069 158,964 150,904
Net investment income 9,471 9,606 18,601 18,558
Products revenues 0 0 0 0
Services and other revenues 82,460 85,177 155,313 181,871
Operating revenues 171,348 172,852 332,878 351,333
Attritional Current Year Claims and Claims Adjustment Expense (48,832) (36,152) (98,774) (79,337)
Catastrophe Current Year Claims and Claims Adjustment Expense 0 0 0 0
Losses and loss adjustment expenses, prior accident year (202) (202) (3,078) 1,068
Amortization of policy acquisition costs (6,234) (6,256) (12,435) (12,002)
Other underwriting expenses (17,452) (19,213) (37,988) (37,278)
Products expenses 0 0 0 0
Services and other expenses (247,568) (32,607) (293,338) (65,751)
Adjusted operating income (loss) (148,940) 78,422 (112,735) 158,033
Net investment gains (losses) 0 0 369 0
Consumer and Other        
Segment Reporting [Line Items]        
Earned premiums 0 0 0 0
Net investment income 0 0 0 0
Products revenues 437,570 422,352 612,266 614,231
Services and other revenues 114,404 106,874 220,205 202,781
Operating revenues 551,974 529,226 832,471 817,012
Attritional Current Year Claims and Claims Adjustment Expense 0 0 0 0
Catastrophe Current Year Claims and Claims Adjustment Expense 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
Products expenses (342,277) (341,098) (499,757) (514,971)
Services and other expenses (87,551) (86,605) (170,813) (168,130)
Adjusted operating income (loss) 122,146 101,523 161,901 133,911
Net investment gains (losses) 0 0 0 0
Corporate and eliminations        
Segment Reporting [Line Items]        
Earned premiums 0 0 0 0
Net investment income 15,429 12,675 32,570 33,301
Products revenues 0 0 0 0
Services and other revenues 7,704 12,442 14,398 17,475
Operating revenues 23,133 25,117 46,968 50,776
Attritional Current Year Claims and Claims Adjustment Expense 0 0 0 0
Catastrophe Current Year Claims and Claims Adjustment Expense 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
Products expenses 0 0 0 0
Services and other expenses (12,142) 0 (32,967) 0
Adjusted operating income (loss) 10,991 25,117 14,001 50,776
Corporate Operations        
Segment Reporting [Line Items]        
Net investment gains (losses) $ 137,241 $ (349) $ (36,776) $ 74,774
[1] Catastrophe current accident year losses and loss adjustment expenses were related to the Middle East conflict.