v3.26.3
Investments - Allowance for Credit Loss (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Rollforward of the allowance for credit loss by major security type        
Beginning balance $ 45.6 $ 3.1 $ 26.9 $ 18.7
Additions for credit losses not previously recorded 10.0 15.7 42.9 16.1
Reductions for securities sold during the period     (0.9)  
Additional increases (decreases) for credit losses on securities with an allowance recorded in the previous period 7.0   12.8 0.1
Write-offs charged against allowance (13.6)   (32.7) (16.2)
Allowance of deconsolidated entities (4.1)   (4.1)  
Foreign currency translation adjustment (0.1) (0.1) (0.1)  
Ending balance 44.8 18.7 44.8 18.7
Accrued interest written off to net investment income   0.4 1.6 0.4
U.S. government and agencies        
Rollforward of the allowance for credit loss by major security type        
Beginning balance     0.1  
Additional increases (decreases) for credit losses on securities with an allowance recorded in the previous period     (0.1)  
Corporate debt securities        
Rollforward of the allowance for credit loss by major security type        
Beginning balance 43.6 2.5 25.0 18.5
Additions for credit losses not previously recorded 9.9 14.9 42.5 14.9
Reductions for securities sold during the period     (0.9)  
Additional increases (decreases) for credit losses on securities with an allowance recorded in the previous period 4.9   10.5 0.1
Write-offs charged against allowance (13.6)   (32.3) (16.2)
Allowance of deconsolidated entities (4.1)   (4.1)  
Foreign currency translation adjustment (0.1) (0.1) (0.1)  
Ending balance 40.6 17.3 40.6 17.3
Accrued interest written off to net investment income   0.4 1.6 0.4
Commercial mortgage-backed securities        
Rollforward of the allowance for credit loss by major security type        
Beginning balance 1.7 0.3 1.4  
Additions for credit losses not previously recorded 0.1 0.8 0.4 1.1
Additional increases (decreases) for credit losses on securities with an allowance recorded in the previous period 2.1   2.5  
Write-offs charged against allowance     (0.4)  
Ending balance 3.9 1.1 3.9 1.1
Collateralized debt obligations        
Rollforward of the allowance for credit loss by major security type        
Beginning balance   0.1    
Additions for credit losses not previously recorded       0.1
Additional increases (decreases) for credit losses on securities with an allowance recorded in the previous period   (0.1)   (0.1)
Other debt obligations        
Rollforward of the allowance for credit loss by major security type        
Beginning balance 0.3 0.2 0.4 0.2
Additional increases (decreases) for credit losses on securities with an allowance recorded in the previous period   0.1 (0.1) 0.1
Ending balance $ 0.3 $ 0.3 $ 0.3 $ 0.3