v3.26.3
Segment Information (Details) - Prior Year Development and Catastrophes - Reportable Segments [Member] - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Segment reporting information        
Net favorable (unfavorable) prior year reserve development $ 234 $ 22 $ 1,225 $ 715
Catastrophe losses 538 402 1,817 3,595
Business Insurance [Member]        
Segment reporting information        
Net favorable (unfavorable) prior year reserve development 41 (125) 522 28
Catastrophe losses 157 139 774 1,016
Bond & Specialty Insurance [Member]        
Segment reporting information        
Net favorable (unfavorable) prior year reserve development 95 43 235 191
Catastrophe losses 1 0 13 24
Personal Insurance [Member]        
Segment reporting information        
Net favorable (unfavorable) prior year reserve development 98 104 468 496
Catastrophe losses $ 380 $ 263 $ 1,030 $ 2,555