v3.25.2
Segments of Operations - Revenues by segment and sub-segment (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Segment Reporting Information [Line Items]        
Net earned premiums $ 1,647 $ 1,585 $ 3,227 $ 3,131
Net investment income 184 188 357 386
Other income 27 27 54 66
Revenues before realized gains (losses) 1,922 1,902 3,775 3,794
Realized gains (losses) on securities 2 (2) 5 12
Total revenues 1,924 1,900 3,780 3,806
Operating segments | Property and Casualty Insurance        
Segment Reporting Information [Line Items]        
Net earned premiums 1,647 1,585 3,227 3,131
Net investment income 179 189 349 394
Other income 0 2 3 4
Revenues before realized gains (losses) 1,826 1,776 3,579 3,529
Operating segments | Property and Casualty Insurance | Property and transportation        
Segment Reporting Information [Line Items]        
Net earned premiums 576 552 1,076 1,072
Operating segments | Property and Casualty Insurance | Specialty casualty        
Segment Reporting Information [Line Items]        
Net earned premiums 799 791 1,593 1,574
Operating segments | Property and Casualty Insurance | Specialty financial        
Segment Reporting Information [Line Items]        
Net earned premiums 272 242 558 485
Operating segments | Other        
Segment Reporting Information [Line Items]        
Revenues before realized gains (losses) $ 96 $ 126 $ 196 $ 265