v3.26.1
Short-Duration Insurance Contracts - Schedule of Reinsurance Reserve Balances (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]        
Beginning gross reserves     $ 565.2  
Claims and claim expense payments for claims occurring during:        
Ending gross reserves $ 587.8   587.8  
Property & Casualty        
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]        
Beginning gross reserves 406.9 $ 416.7 404.5 $ 420.6
Less: reinsurance recoverables 101.5 98.3 101.2 100.8
Net reserves, beginning of period 305.4 318.4 303.3 319.8
Incurred claims and claim expenses:        
Claims occurring in the current period 134.0 141.9 253.1 265.7
Increase (decrease) in estimated reserves for claims occurring in prior periods (6.6) (5.5) (11.6) (10.8)
Total claims and claim expenses incurred 127.4 136.4 241.5 254.9
Claims and claim expense payments for claims occurring during:        
Current period 78.8 89.7 123.6 139.7
Prior periods 39.2 44.0 106.4 113.9
Total claims and claim expense payments 118.0 133.7 230.0 253.6
Net reserves, end of period 314.8 321.0 314.8 321.0
Plus: reinsurance recoverables 100.6 98.8 100.6 98.8
Ending gross reserves 415.4 419.8 415.4 419.8
Group Benefits        
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]        
Beginning gross reserves 116.7 109.0 113.2 104.9
Less: reinsurance recoverables 27.0 25.9 26.5 25.2
Net reserves, beginning of period 89.7 83.1 86.7 79.7
Incurred claims and claim expenses:        
Claims occurring in the current period 24.2 18.6 46.0 37.0
Increase (decrease) in estimated reserves for claims occurring in prior periods (1.6) (3.0) (4.3) (2.6)
Total claims and claim expenses incurred 22.6 15.6 41.7 34.4
Claims and claim expense payments for claims occurring during:        
Current period 11.6 5.9 16.3 9.7
Prior periods 9.0 5.4 20.3 17.0
Total claims and claim expense payments 20.6 11.3 36.6 26.7
Net reserves, end of period 91.7 87.4 91.7 87.4
Plus: reinsurance recoverables 27.7 25.8 27.7 25.8
Ending gross reserves $ 119.4 $ 113.2 $ 119.4 $ 113.2