v3.25.2
Reserve for Property and Casualty Insurance Claims and Claims Expense - Schedule of Prior Year Reserve Re-Estimates Included in Claims and Claims Expense (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Increase (decrease) in claims and claims expense        
Prior years $ (370) $ (203) $ (621) $ (354)
Auto        
Increase (decrease) in claims and claims expense        
Prior years (431) (180) (680) (254)
Homeowners        
Increase (decrease) in claims and claims expense        
Prior years 30 (191) 22 (380)
Other personal lines        
Increase (decrease) in claims and claims expense        
Prior years 30 61 76 113
Commercial lines        
Increase (decrease) in claims and claims expense        
Prior years 9 107 (19) 158
Other business lines        
Increase (decrease) in claims and claims expense        
Prior years (10) (1) (25) 4
Run-off Property-Liability        
Increase (decrease) in claims and claims expense        
Prior years 2 2 5 6
Protection Services        
Increase (decrease) in claims and claims expense        
Prior years 0 (1) 0 (1)
Catastrophe losses        
Increase (decrease) in claims and claims expense        
Prior years 6 (138) (10) (300)
Catastrophe losses | Auto        
Increase (decrease) in claims and claims expense        
Prior years (16) (9) (27) (16)
Catastrophe losses | Homeowners        
Increase (decrease) in claims and claims expense        
Prior years 18 (128) 17 (277)
Catastrophe losses | Other personal lines        
Increase (decrease) in claims and claims expense        
Prior years 2 1 (5) (2)
Catastrophe losses | Commercial lines        
Increase (decrease) in claims and claims expense        
Prior years 2 (2) 5 (5)
Catastrophe losses | Other business lines        
Increase (decrease) in claims and claims expense        
Prior years 0 0 0 0
Catastrophe losses | Run-off Property-Liability        
Increase (decrease) in claims and claims expense        
Prior years 0 0 0 0
Catastrophe losses | Protection Services        
Increase (decrease) in claims and claims expense        
Prior years 0 0 0 0
Non-catastrophe losses        
Increase (decrease) in claims and claims expense        
Prior years (376) (65) (611) (54)
Non-catastrophe losses | Auto        
Increase (decrease) in claims and claims expense        
Prior years (415) (171) (653) (238)
Non-catastrophe losses | Homeowners        
Increase (decrease) in claims and claims expense        
Prior years 12 (63) 5 (103)
Non-catastrophe losses | Other personal lines        
Increase (decrease) in claims and claims expense        
Prior years 28 60 81 115
Non-catastrophe losses | Commercial lines        
Increase (decrease) in claims and claims expense        
Prior years 7 109 (24) 163
Non-catastrophe losses | Other business lines        
Increase (decrease) in claims and claims expense        
Prior years (10) (1) (25) 4
Non-catastrophe losses | Run-off Property-Liability        
Increase (decrease) in claims and claims expense        
Prior years 2 2 5 6
Non-catastrophe losses | Protection Services        
Increase (decrease) in claims and claims expense        
Prior years $ 0 $ (1) 0 $ (1)
Nationwide Reinsurance Program | Run-off Property-Liability        
Increase (decrease) in claims and claims expense        
Prior years     $ 60