v3.26.1
Investments - Net Investment Income (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Net Investment Income [Line Items]        
Total net investment income $ 120.5 $ 110.8 $ 231.2 $ 226.7
Investment Portfolio        
Net Investment Income [Line Items]        
Investment expenses (2.3) (3.1) (5.4) (5.9)
Total net investment income 96.2 85.7 183.3 177.2
Deposit Asset on Reinsurance        
Net Investment Income [Line Items]        
Total net investment income 24.3 25.1 47.9 49.5
Fixed maturity securities | Investment Portfolio        
Net Investment Income [Line Items]        
Net investment income 75.2 59.4 146.4 131.0
Equity securities | Investment Portfolio        
Net Investment Income [Line Items]        
Net investment income 0.8 1.0 1.3 2.0
Limited partnership interests | Investment Portfolio        
Net Investment Income [Line Items]        
Net investment income 17.2 23.2 30.4 39.5
Short-term and other investments | Investment Portfolio        
Net Investment Income [Line Items]        
Net investment income $ 5.3 $ 5.2 $ 10.6 $ 10.6