v3.25.4
Business Segments - Segment Expenses (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Segment Reporting Information [Line Items]      
Policy Acquisition Costs $ 678.2 $ 641.6 $ 707.6
Business Unit Operating Costs 310.7 277.4 256.1
Corporate Overhead Costs 178.5 194.9 200.0
Insurance Expenses 1,167.4 1,113.9 1,163.7
Income Tax Expense (Benefit) 28.1 76.0 (74.8)
Total Expenses 4,629.0 4,250.1 5,291.3
Operating Segments      
Segment Reporting Information [Line Items]      
Total Expenses 4,473.4 3,911.2 4,393.7
Operating Segments | Specialty Property & Casualty Insurance      
Segment Reporting Information [Line Items]      
Total Incurred Losses and LAE 3,077.2 2,541.7 3,141.9
Policy Acquisition Costs 539.4 478.7 496.4
Business Unit Operating Costs 160.9 145.0 107.8
Corporate Overhead Costs 136.3 135.8 137.1
Insurance Expenses 836.6 759.5 741.3
Income Tax Expense (Benefit) 44.9 94.6 (19.2)
Total Expenses 3,958.7 3,395.8 3,864.0
Operating Segments | Specialty Property & Casualty Insurance | Non-catastrophe Losses      
Segment Reporting Information [Line Items]      
Current Year 2,991.1 2,514.8 2,974.5
Prior Years 74.8 6.3 135.2
Operating Segments | Specialty Property & Casualty Insurance | Catastrophe Losses      
Segment Reporting Information [Line Items]      
Current Year 11.5 19.9 34.5
Prior Years (0.2) 0.7 (2.3)
Operating Segments | Life Insurance      
Segment Reporting Information [Line Items]      
Policyholders’ Benefits and Incurred Losses and LAE 238.7 234.5 243.4
Policy Acquisition Costs 129.1 133.9 140.0
Business Unit Operating Costs 101.6 96.9 96.7
Corporate Overhead Costs 33.7 41.3 39.1
Insurance Expenses 264.4 272.1 275.8
Income Tax Expense (Benefit) 11.6 8.8 10.5
Total Expenses $ 514.7 $ 515.4 $ 529.7