v3.26.3
Other Comprehensive Income (Loss) (Reclassifications out of Accumulated Other Comprehensive (Loss) 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 realized losses from sales and other $ (8.3) $ (20.3) $ (18.6) $ (43.7)
Income from continuing operations before income taxes 220.3 227.1 702.0 586.0
Income tax (expense) benefit (48.0) (48.5) (151.5) (122.3)
Income from discontinued life businesses 0.3 0.1 0.5 0.3
Income from continuing operations (172.3) (178.6) (550.5) (463.7)
Net income 172.6 178.7 551.0 464.0
Reclassification out of Accumulated Other Comprehensive Loss [Member]        
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]        
Net income (8.9) (17.5) (21.4) (38.4)
Net Unrealized Appreciation (Depreciation) on Investments [Member] | Reclassification out of Accumulated Other Comprehensive Loss [Member]        
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]        
Net realized losses from sales and other (8.3) (20.3) (19.6) (44.0)
Recoveries (impairments) on investments (1.8) 0.1 (3.3) (0.1)
Income from continuing operations before income taxes (10.1) (20.2) (22.9) (44.1)
Income tax (expense) benefit 2.5 4.2 5.3 9.9
Income from continuing operations (7.6) (16.0) (17.6) (34.2)
Net income (7.6) (16.2) (17.8) (34.6)
Net Unrealized Appreciation (Depreciation) on Investments [Member] | Reclassification out of Accumulated Other Comprehensive Loss [Member] | Life [Member]        
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]        
Income from discontinued life businesses 0.1 0.0 0.5 0.2
Defined Benefit Pension and Postretirement Plans [Member] | Reclassification out of Accumulated Other Comprehensive Loss [Member]        
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]        
Income from continuing operations before income taxes 1.7 1.7 5.1 5.0
Income tax (expense) benefit 0.3 0.4 1.0 1.0
Income from continuing operations (1.4) (1.3) (4.1) (4.0)
Net change in market risk | Reclassification out of Accumulated Other Comprehensive Loss [Member]        
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]        
Income tax (expense) benefit (0.1) 0.0 (0.2) (0.1)
Income from discontinued life businesses (0.0) (0.2) (0.2) (0.4)
Net change in market risk | Reclassification out of Accumulated Other Comprehensive Loss [Member] | Life [Member]        
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]        
Income from discontinued life businesses $ 0.2 $ 0.0 $ 0.7 $ 0.3