v3.26.3
Comprehensive Income (Loss) - Schedule of Reclassification out of AOCI (Details) - USD ($)
$ in Thousands
 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 realized and unrealized investment gains (losses) $ (19,446) $ 8,057 $ (15,776) $ 12,458
Loss and loss expense incurred 762,696 819,031 2,394,466 2,389,254
Other insurance expenses 143,828 127,487 414,704 375,180
Income (loss) before income tax 162,088 145,711 449,135 393,502
Total income tax expense (benefit) (33,436) (30,371) (93,422) (82,323)
Net income (loss) 128,652 115,340 355,713 311,179
Reclassification out of AOCI        
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]        
Net income (loss) 14,803 493 27,445 114
Reclassification out of AOCI | Net realized (gains) losses on disposals and intent-to-sell AFS securities        
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]        
Net realized and unrealized investment gains (losses) 5,055 580 10,036 (128)
Total income tax expense (benefit) (1,062) (122) (2,108) 27
Net income (loss) 3,993 458 7,928 (101)
Reclassification out of AOCI | Credit loss related        
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]        
Net realized and unrealized investment gains (losses) 12,876 (829) 22,285 (2,345)
Total income tax expense (benefit) (2,704) 174 (4,680) 492
Net income (loss) 10,172 (655) 17,605 (1,853)
Reclassification out of AOCI | Defined benefit pension and post-retirement life plans        
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]        
Loss and loss expense incurred 186 201 557 602
Other insurance expenses 621 671 1,863 2,015
Income (loss) before income tax 807 872 2,420 2,617
Total income tax expense (benefit) (169) (182) (508) (549)
Net income (loss) $ 638 $ 690 $ 1,912 $ 2,068