v3.26.1
OTHER COMPREHENSIVE INCOME (LOSS) - Schedule of Amount Reclassified from Accumulated Other Comprehensive Income (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]        
Net gains (losses) on investments $ (8) $ (5) $ (17) $ (12)
Income tax expense (benefit) (124) (135) (207) (173)
Other underwriting expenses (225) (254) (441) (492)
Net income (loss) 559 680 1,213 890
URA(D) of securities | Reclassification From Accumulated Other Comprehensive Income        
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]        
Net gains (losses) on investments 13 10 16 15
Income tax expense (benefit) (1) (3) (3) (3)
Net income (loss) 12 7 13 12
Benefit plan net gain (loss) | Reclassification From Accumulated Other Comprehensive Income        
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]        
Income tax expense (benefit) 0 6 0 6
Other underwriting expenses 0 (28) (1) (28)
Net income (loss) $ 0 $ (22) $ (1) $ (22)