v3.26.1
Segment Reporting Disclosures (Company's Segment Disclosures) (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Segment Reporting Information [Line Items]    
Earned premiums $ 2,048,886 $ 2,089,374
Net investment income 255,890 237,095
Products revenues 572,421 561,124
Services and other revenues 673,408 660,583
Operating revenues 3,550,605 3,548,176
Attritional Current Year Claims and Claims Adjustment Expense (1,235,852) (1,338,708)
Catastrophe Current Year Claims and Claims Adjustment Expense (35,028) [1] (66,064)
Losses and loss adjustment expenses, prior accident year 104,063 150,107
Amortization of policy acquisition costs (412,930) (417,022)
Other underwriting expenses (326,898) (330,416)
Products expenses (517,430) (499,908)
Services and other expenses (628,784) (567,628)
Adjusted operating income (loss) 497,746 478,537
Net investment gains (losses) (727,562) (149,071)
Amortization of acquired intangible assets (43,513) (46,942)
Interest expense (50,886) (52,140)
Net foreign exchange gains (losses) 54,277 (72,633)
Income (Loss) before income taxes (269,938) 157,751
Markel Insurance    
Segment Reporting Information [Line Items]    
Earned premiums 1,969,339 2,016,539
Net investment income 229,619 207,517
Products revenues 0 0
Services and other revenues 2,727 2,620
Operating revenues 2,201,685 2,226,676
Attritional Current Year Claims and Claims Adjustment Expense (1,185,910) (1,295,523)
Catastrophe Current Year Claims and Claims Adjustment Expense (35,028) [1] (66,064)
Losses and loss adjustment expenses, prior accident year 106,939 148,837
Amortization of policy acquisition costs (406,729) (411,276)
Other underwriting expenses (306,362) (312,351)
Products expenses 0 0
Services and other expenses (5,105) (8,184)
Adjusted operating income (loss) 369,490 282,115
Net investment gains (losses) (553,914) (224,194)
Industrial    
Segment Reporting Information [Line Items]    
Earned premiums 0 0
Net investment income 0 0
Products revenues 397,725 369,245
Services and other revenues 485,333 460,329
Operating revenues 883,058 829,574
Attritional Current Year Claims and Claims Adjustment Expense 0 0
Catastrophe Current Year Claims and Claims Adjustment Expense 0 0
Losses and loss adjustment expenses, prior accident year 0 0
Amortization of policy acquisition costs 0 0
Other underwriting expenses 0 0
Products expenses (359,950) (326,035)
Services and other expenses (473,822) (444,775)
Adjusted operating income (loss) 49,286 58,764
Net investment gains (losses) 0 0
Financial    
Segment Reporting Information [Line Items]    
Earned premiums 79,547 72,835
Net investment income 9,130 8,952
Products revenues 0 0
Services and other revenues 72,853 96,694
Operating revenues 161,530 178,481
Attritional Current Year Claims and Claims Adjustment Expense (49,942) (43,185)
Catastrophe Current Year Claims and Claims Adjustment Expense 0 0
Losses and loss adjustment expenses, prior accident year (2,876) 1,270
Amortization of policy acquisition costs (6,201) (5,746)
Other underwriting expenses (20,536) (18,065)
Products expenses 0 0
Services and other expenses (45,770) (33,144)
Adjusted operating income (loss) 36,205 79,611
Net investment gains (losses) 369 0
Consumer and Other    
Segment Reporting Information [Line Items]    
Earned premiums 0 0
Net investment income 0 0
Products revenues 174,696 191,879
Services and other revenues 105,801 95,907
Operating revenues 280,497 287,786
Attritional Current Year Claims and Claims Adjustment Expense 0 0
Catastrophe Current Year Claims and Claims Adjustment Expense 0 0
Losses and loss adjustment expenses, prior accident year 0 0
Amortization of policy acquisition costs 0 0
Other underwriting expenses 0 0
Products expenses (157,480) (173,873)
Services and other expenses (83,262) (81,525)
Adjusted operating income (loss) 39,755 32,388
Net investment gains (losses) 0 0
Corporate and eliminations    
Segment Reporting Information [Line Items]    
Earned premiums 0 0
Net investment income 17,141 20,626
Products revenues 0 0
Services and other revenues 6,694 5,033
Operating revenues 23,835 25,659
Attritional Current Year Claims and Claims Adjustment Expense 0 0
Catastrophe Current Year Claims and Claims Adjustment Expense 0 0
Losses and loss adjustment expenses, prior accident year 0 0
Amortization of policy acquisition costs 0 0
Other underwriting expenses 0 0
Products expenses 0 0
Services and other expenses (20,825) 0
Adjusted operating income (loss) 3,010 25,659
Corporate Operations    
Segment Reporting Information [Line Items]    
Net investment gains (losses) $ (174,017) $ 75,123
[1] Catastrophe current accident year losses and loss adjustment expenses were attributable to the Middle East conflict.