v3.26.3
Reserves - Roll Forward of Claims and Benefits Payable (Details) - USD ($)
$ in Millions
 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]    
Claims and benefits payable, at beginning of period $ 2,101.2 $ 2,914.2
Less: Reinsurance ceded and other (899.0) (1,669.8)
Net claims and benefits payable, at beginning of period 1,202.2 1,244.4
Incurred losses and loss adjustment expenses related to:    
Current Year Claims and Claims Adjustment Expense 2,397.2 2,337.0
Prior years (97.4) (126.2)
Total incurred losses and loss adjustment expenses 2,299.8 2,210.8
Paid losses and loss adjustment expenses related to:    
Current year 1,618.7 1,596.3
Prior years 622.1 635.3
Total paid losses and loss adjustment expenses 2,240.8 2,231.6
Net claims and benefits payable, at end of period 1,261.2 1,223.6
Plus: Reinsurance ceded and other 825.6 988.4
Claims and benefits payable, at end of period 2,086.8 2,212.0
Ceded to U.S. Government | Not Rated    
Liability for Claims and Claims Adjustment Expense [Line Items]    
Reinsurance recoverables $ 128.8 $ 256.0