v3.25.1
Basis of Presentation (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Jan. 01, 2025
Dec. 31, 2024
Dec. 31, 2023
Accounting changes          
Equity $ 18,034 $ 16,998   $ 17,937 $ 16,525
Retained Earnings          
Accounting changes          
Equity $ 16,821 $ 16,060   16,459 $ 15,617
Cumulative Effect, Period of Adoption, Adjustment          
Accounting changes          
Equity       5  
Cumulative Effect, Period of Adoption, Adjustment | Retained Earnings          
Accounting changes          
Equity     $ 5 $ 5  
Share-Based Payment Arrangement          
Basis of Presentation [Abstract]          
Shares excluded from diluted EPS calculation (in shares) 1,200,000 0      
CNA          
Basis of Presentation [Abstract]          
Subsidiary ownership (as a percent) 92.00%