v3.26.3
Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Net income $ 172.6 $ 178.7 $ 551.0 $ 464.0
Changes in net unrealized gains (losses) on investment securities:        
Having no credit losses recognized in the Consolidated Statements of Income (301.4) 88.3 (389.3) 255.8
Having credit losses recognized in the Consolidated Statements of Income (0.2) 0.1 0.1 0.1
Total available-for-sale securities (301.6) 88.4 (389.2) 255.9
Pension and postretirement benefits:        
Net amount recognized as net periodic benefit cost 172.3 178.6 550.5 463.7
Long-duration insurance contracts:        
Net change in market risk 2.8 (0.8) 3.4 (1.9)
Total other comprehensive income (loss), net of tax (297.4) 88.9 (381.7) 258.0
Comprehensive income (loss) (124.8) 267.6 169.3 722.0
Reclassification out of Accumulated Other Comprehensive Loss [Member]        
Net income (8.9) (17.5) (21.4) (38.4)
Defined Benefit Pension and Postretirement Plans [Member] | Reclassification out of Accumulated Other Comprehensive Loss [Member]        
Pension and postretirement benefits:        
Net amount recognized as net periodic benefit cost $ 1.4 $ 1.3 $ 4.1 $ 4.0