v3.25.2
Short-Duration Insurance Contracts - Schedule of Reinsurance Reserve Balances (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]        
Beginning gross reserves     $ 569.2  
Incurred claims and claim expenses:        
Total claims and claim expenses incurred $ 17.1 $ 18.1 33.4 $ 35.5
Claims and claim expense payments for claims occurring during:        
Ending gross reserves 576.6   576.6  
Property & Casualty        
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]        
Beginning gross reserves 416.7 418.2 420.6 416.8
Less: reinsurance recoverables 98.3 103.6 100.8 104.0
Net reserves, beginning of period 318.4 314.6 319.8 312.8
Incurred claims and claim expenses:        
Claims occurring in the current period 141.9 159.0 265.7 283.7
Increase (decrease) in estimated reserves for claims occurring in prior periods (5.5) (6.2) (10.8) (6.2)
Total claims and claim expenses incurred 136.4 152.8 254.9 277.5
Claims and claim expense payments for claims occurring during:        
Current period 89.7 94.2 139.7 138.7
Prior periods 44.0 42.0 113.9 120.4
Total claims and claim expense payments 133.7 136.2 253.6 259.1
Net reserves, end of period 321.0 331.2 321.0 331.2
Plus: reinsurance recoverables 98.8 101.7 98.8 101.7
Ending gross reserves 419.8 432.9 419.8 432.9
Group Benefits        
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]        
Beginning gross reserves 109.0 114.3 104.9 116.6
Less: reinsurance recoverables 25.9 27.6 25.2 27.7
Net reserves, beginning of period 83.1 86.7 79.7 88.9
Incurred claims and claim expenses:        
Claims occurring in the current period 18.6 19.4 37.0 39.6
Increase (decrease) in estimated reserves for claims occurring in prior periods (3.0) (3.3) (2.6) (9.4)
Total claims and claim expenses incurred 15.6 16.1 34.4 30.2
Claims and claim expense payments for claims occurring during:        
Current period 5.9 8.2 9.7 12.1
Prior periods 5.4 6.5 17.0 18.9
Total claims and claim expense payments 11.3 14.7 26.7 31.0
Net reserves, end of period 87.4 88.1 87.4 88.1
Plus: reinsurance recoverables 25.8 28.0 25.8 28.0
Ending gross reserves $ 113.2 $ 116.1 $ 113.2 $ 116.1