v3.25.3
Insurance Claim Reserves (Details) - Prior Year Reserve Development - Property-casualty [Member] - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Liability for claims and claim adjustment expense        
Net favorable development included in estimated claims and claim adjustment expenses incurred for claims arising in prior years     $ 648 $ 321
Net favorable (unfavorable) prior year reserve development impacting the Company's results of operations     715 447
Accretion expense     32 33
Business Insurance [Member]        
Liability for claims and claim adjustment expense        
Net favorable (unfavorable) prior year reserve development impacting the Company's results of operations $ (125) $ (91) 28 (57)
Business Insurance [Member] | Asbestos reserves [Member]        
Liability for claims and claim adjustment expense        
Increase to reserves 277 242 277 242
Bond & Specialty Insurance [Member]        
Liability for claims and claim adjustment expense        
Net favorable (unfavorable) prior year reserve development impacting the Company's results of operations 43 36 191 84
Personal Insurance [Member]        
Liability for claims and claim adjustment expense        
Net favorable (unfavorable) prior year reserve development impacting the Company's results of operations $ 104 $ 181 $ 496 $ 420