v3.26.3
OTHER COMPREHENSIVE INCOME (LOSS) - Schedule of Amount Reclassified from Accumulated Other Comprehensive Income (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]        
Net gains (losses) on investments $ (68) $ (47) $ (86) $ (59)
Income tax expense (benefit) (36) (14) (243) (187)
Other underwriting expenses (200) (258) (641) (750)
Net income (loss) 233 255 1,445 1,145
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 60 47 76 62
Income tax expense (benefit) (16) (10) (19) (14)
Net income (loss) 44 37 57 48
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 0 0 2
Other underwriting expenses 0 0 (1) (10)
Net income (loss) $ 0 $ 0 $ (1) $ (8)