v3.25.2
Fair Value of Financial Instruments - Rollforward of Instruments Measured on Recurring Basis (Details) - Level 3 - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Financial Assets        
Beginning balance $ 523.0 $ 509.9 $ 533.0 $ 518.5
Transfers into Level 3 0.0 0.0 0.0 0.0
Transfers out of Level 3 0.0 0.0 0.0 (4.4)
Total gains or losses        
Net investment gains (losses) included in net income (0.9) 0.2 4.9 0.3
Net unrealized gains (losses) included in OCI 2.8 (1.2) 3.0 (0.1)
Purchases 8.9 29.4 22.3 43.5
Issuances 0.0 0.0 0.0 0.0
Sales (4.7) 0.0 (27.1) 0.0
Settlements 0.0 0.0 0.0 0.0
Paydowns, maturities and distributions (10.1) (11.7) (17.1) (31.2)
Ending balance 519.0 526.6 519.0 526.6
Financial Liabilities        
Beginning balance 74.3 80.8 75.5 82.4
Transfers into Level 3 0.0 0.0 0.0 0.0
Transfers out of Level 3 0.0 0.0 0.0 0.0
Total gains or losses        
Net investment (gains) losses included in net income related to financial liabilities 3.7 (0.3) 5.6 1.0
Net unrealized gains (losses) included in OCI (0.4) 0.1 (0.2) 0.0
Purchases 0.0 0.0 0.0 0.0
Issuances 0.7 1.4 2.1 2.8
Sales 0.0 0.0 0.0 0.0
Settlements 0.0 0.0 0.0 0.0
Paydowns, maturities and distributions (4.3) (4.1) (9.0) (8.3)
Ending balance $ 74.0 $ 77.9 $ 74.0 $ 77.9
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Net investment gains (losses) Net investment gains (losses) Net investment gains (losses) Net investment gains (losses)
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Liability, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration] Other Comprehensive Income (Loss), Available-for-Sale Securities Adjustment, Net of Tax, Portion Attributable to Parent Other Comprehensive Income (Loss), Available-for-Sale Securities Adjustment, Net of Tax, Portion Attributable to Parent Other Comprehensive Income (Loss), Available-for-Sale Securities Adjustment, Net of Tax, Portion Attributable to Parent Other Comprehensive Income (Loss), Available-for-Sale Securities Adjustment, Net of Tax, Portion Attributable to Parent
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Asset, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration] Other Comprehensive Income (Loss), Available-for-Sale Securities Adjustment, Net of Tax, Portion Attributable to Parent Other Comprehensive Income (Loss), Available-for-Sale Securities Adjustment, Net of Tax, Portion Attributable to Parent Other Comprehensive Income (Loss), Available-for-Sale Securities Adjustment, Net of Tax, Portion Attributable to Parent Other Comprehensive Income (Loss), Available-for-Sale Securities Adjustment, Net of Tax, Portion Attributable to Parent
Municipal bonds        
Financial Assets        
Beginning balance $ 76.1 $ 73.2 $ 74.9 $ 74.0
Transfers into Level 3 0.0 0.0 0.0 0.0
Transfers out of Level 3 0.0 0.0 0.0 0.0
Total gains or losses        
Net investment gains (losses) included in net income 0.0 0.0 0.0 0.0
Net unrealized gains (losses) included in OCI 0.1 (0.7) 1.5 (1.4)
Purchases 0.0 0.0 0.0 0.0
Issuances 0.0 0.0 0.0 0.0
Sales 0.0 0.0 0.0 0.0
Settlements 0.0 0.0 0.0 0.0
Paydowns, maturities and distributions (0.3) (0.4) (0.5) (0.5)
Ending balance 75.9 72.1 75.9 72.1
Corporate bonds        
Financial Assets        
Beginning balance 340.9 345.5 351.3 342.5
Transfers into Level 3 0.0 0.0 0.0 0.0
Transfers out of Level 3 0.0 0.0 0.0 (4.4)
Total gains or losses        
Net investment gains (losses) included in net income 0.0 (0.8) 0.0 (0.8)
Net unrealized gains (losses) included in OCI 2.4 0.4 1.8 (0.2)
Purchases 8.9 27.6 22.3 41.7
Issuances 0.0 0.0 0.0 0.0
Sales (3.0) 0.0 (25.3) 0.0
Settlements 0.0 0.0 0.0 0.0
Paydowns, maturities and distributions (7.3) (6.3) (8.1) (12.4)
Ending balance 342.0 366.4 342.0 366.4
Mortgage Backed and Other Asset- Backed Securities        
Financial Assets        
Beginning balance 67.1 88.7 73.7 97.5
Transfers into Level 3 0.0 0.0 0.0 0.0
Transfers out of Level 3 0.0 0.0 0.0 0.0
Total gains or losses        
Net investment gains (losses) included in net income 0.0 0.8 0.0 0.8
Net unrealized gains (losses) included in OCI 0.3 (0.9) (0.2) 1.5
Purchases 0.0 1.8 0.0 1.8
Issuances 0.0 0.0 0.0 0.0
Sales (1.7) 0.0 (1.8) 0.0
Settlements 0.0 0.0 0.0 0.0
Paydowns, maturities and distributions (2.5) (5.0) (8.5) (16.2)
Ending balance 63.2 85.4 63.2 85.4
Total Fixed Maturity Securities        
Financial Assets        
Beginning balance 484.1 507.4 499.9 514.0
Transfers into Level 3 0.0 0.0 0.0 0.0
Transfers out of Level 3 0.0 0.0 0.0 (4.4)
Total gains or losses        
Net investment gains (losses) included in net income 0.0 0.0 0.0 0.0
Net unrealized gains (losses) included in OCI 2.8 (1.2) 3.0 (0.1)
Purchases 8.9 29.4 22.3 43.5
Issuances 0.0 0.0 0.0 0.0
Sales (4.7) 0.0 (27.1) 0.0
Settlements 0.0 0.0 0.0 0.0
Paydowns, maturities and distributions (10.1) (11.7) (17.1) (29.1)
Ending balance 481.0 523.9 481.0 523.9
Equity Securities & Limited Partnership Interests        
Financial Assets        
Beginning balance 38.9 2.5 33.1 4.5
Transfers into Level 3 0.0 0.0 0.0 0.0
Transfers out of Level 3 0.0 0.0 0.0 0.0
Total gains or losses        
Net investment gains (losses) included in net income (0.9) 0.2 4.9 0.3
Net unrealized gains (losses) included in OCI 0.0 0.0 0.0 0.0
Purchases 0.0 0.0 0.0 0.0
Issuances 0.0 0.0 0.0 0.0
Sales 0.0 0.0 0.0 0.0
Settlements 0.0 0.0 0.0 0.0
Paydowns, maturities and distributions 0.0 0.0 0.0 (2.1)
Ending balance $ 38.0 $ 2.7 $ 38.0 $ 2.7