v3.26.1
Accumulated Other Comprehensive Income (Loss) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Net unrealized investment gains (losses) on fixed maturity securities, net of tax        
Beginning of period     $ 1,482.7  
Other comprehensive income (loss) before reclassifications $ 0.7 $ 2.1 (19.5) $ 33.3
Amounts reclassified from AOCI 0.1 3.2 (0.3) 3.1
Net current period other comprehensive income (loss) 0.8 5.3 (19.8) 36.4
End of period 1,502.9 1,360.3 1,502.9 1,360.3
Pretax amounts reclassified from AOCI (0.1) (4.1) 0.4 (3.9)
Income tax expense (benefit) amounts reclassified from AOCI 0.0 (0.9) 0.1 (0.8)
Total        
Net unrealized investment gains (losses) on fixed maturity securities, net of tax        
Beginning of period (175.2) (222.4) (154.6) (253.5)
End of period (174.4) (217.1) (174.4) (217.1)
Net Unrealized Investment Gains (Losses) on Fixed Maturity Securities        
Net unrealized investment gains (losses) on fixed maturity securities, net of tax        
Beginning of period (288.8) (314.5) (245.5) (357.4)
Other comprehensive income (loss) before reclassifications 6.8 1.4 (36.1) 44.4
Amounts reclassified from AOCI 0.1 3.2 (0.3) 3.1
Net current period other comprehensive income (loss) 6.9 4.6 (36.4) 47.5
End of period (281.9) (309.9) (281.9) (309.9)
Net Reserve Remeasurements Attributable to Discount Rates        
Net unrealized investment gains (losses) on fixed maturity securities, net of tax        
Beginning of period 116.1 99.1 93.4 110.9
Other comprehensive income (loss) before reclassifications (6.1) 0.7 16.6 (11.1)
Amounts reclassified from AOCI 0.0 0.0 0.0 0.0
Net current period other comprehensive income (loss) (6.1) 0.7 16.6 (11.1)
End of period 110.0 99.8 110.0 99.8
Net Funded Status of Benefit Plans        
Net unrealized investment gains (losses) on fixed maturity securities, net of tax        
Beginning of period (2.5) (7.0) (2.5) (7.0)
Other comprehensive income (loss) before reclassifications 0.0 0.0 0.0 0.0
Amounts reclassified from AOCI 0.0 0.0 0.0 0.0
Net current period other comprehensive income (loss) 0.0 0.0 0.0 0.0
End of period $ (2.5) $ (7.0) $ (2.5) $ (7.0)