v3.26.1
Other Comprehensive Income (Loss) (Reclassifications out of Accumulated Other Comprehensive (Loss) 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 realized losses from sales and other $ (5.4) $ (4.6) $ (10.3) $ (23.4)
Income from continuing operations before income taxes 244.6 198.8 481.7 358.9
Income tax (expense) benefit (53.2) (41.9) (103.5) (73.8)
Income from discontinued life businesses 0.2 0.2 0.2 0.2
Income from continuing operations (191.4) (156.9) (378.2) (285.1)
Net income 191.6 157.1 378.4 285.3
Reclassification out of Accumulated Other Comprehensive Loss [Member]        
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]        
Net income (6.4) (5.1) (12.5) (20.9)
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 (5.7) (4.9) (11.3) (23.7)
Impairments on investments (1.0) (0.3) (1.5) (0.2)
Income from continuing operations before income taxes (6.7) (5.2) (12.8) (23.9)
Income tax (expense) benefit 1.4 1.4 2.8 5.7
Net income (5.3) (3.8) (10.2) (18.4)
Net Unrealized Appreciation (Depreciation) on Investments [Member] | Reclassification out of Accumulated Other Comprehensive Loss [Member] | Accelerated Share Repurchase Agreement [Member]        
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]        
Income from continuing operations (5.3) (3.8) (10.0) (18.2)
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 0.2 0.0 0.4 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 1.6 3.4 3.3
Income tax (expense) benefit 0.4 0.3 0.7 0.6
Income from continuing operations (1.3) (1.3) (2.7) (2.7)
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 0.0 0.0 (0.1) (0.1)
Income from discontinued life businesses (0.0) (0.0) (0.2) (0.2)
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 $ 0.5 $ 0.3