v3.25.4
Income from Investments - Net Investment Income (Details) - USD ($)
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Net Investment Income [Line Items]      
Investment income $ 431,500,000 $ 434,200,000 $ 447,100,000
Investment expenses 26,500,000 26,700,000 27,400,000
Net investment income 405,000,000.0 407,500,000 419,700,000
Interest on Fixed Income Securities      
Net Investment Income [Line Items]      
Investment income 309,400,000 315,300,000 323,300,000
Dividends on Equity Securities Excluding Alternative Investments      
Net Investment Income [Line Items]      
Investment income 8,000,000.0 5,400,000 4,400,000
Total Alternative Investments      
Net Investment Income [Line Items]      
Investment income 6,700,000 6,300,000 29,500,000
Equity Method Limited Liability Investments      
Net Investment Income [Line Items]      
Investment income     10,500,000
Investment expenses 7,000,000.0 18,200,000  
Limited Liability Investments Included in Equity Securities      
Net Investment Income [Line Items]      
Investment income 13,700,000 24,500,000 19,000,000.0
Short-term Investments      
Net Investment Income [Line Items]      
Investment income 22,800,000 33,500,000 18,000,000.0
Loans to Policyholders      
Net Investment Income [Line Items]      
Investment income 20,800,000 21,000,000.0 20,900,000
Real Estate      
Net Investment Income [Line Items]      
Investment income 9,400,000 8,800,000 8,900,000
Investment expenses 9,000,000.0 8,700,000 8,800,000
Other      
Net Investment Income [Line Items]      
Investment income 11,500,000 8,200,000 12,900,000
Investment expenses 17,500,000 18,000,000.0 18,600,000
Cash Surrender Value      
Net Investment Income [Line Items]      
Investment income 42,900,000 35,700,000 29,200,000
Universal Life-type Policyholder Account Balances      
Net Investment Income [Line Items]      
Interest Expense, Other Short-Term Borrowings $ 18,700,000 $ 20,300,000 $ 22,700,000