v3.26.1
Segment Information - Schedule of Return on Equity (Details)
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Segment Reporting [Line Items]        
ROE 14.80% 10.70% 13.00% 12.50%
Operating Segments | Insurance Operations        
Segment Reporting [Line Items]        
ROE 2.30% (0.20%) 2.10% 2.20%
Operating Segments | Standard Commercial Lines        
Segment Reporting [Line Items]        
ROE 0.70% (2.60%) 0.30% 0.40%
Operating Segments | Standard Personal Lines        
Segment Reporting [Line Items]        
ROE 0.40% 0.90% 0.50% 0.50%
Operating Segments | E&S Lines        
Segment Reporting [Line Items]        
ROE 1.20% 1.50% 1.30% 1.30%
Operating Segments | Investments        
Segment Reporting [Line Items]        
Net investment income earned 13.90% 13.00% 13.60% 12.90%
Net realized and unrealized investment gains (losses) 1.10% 0.40% 0.20% 0.20%
ROE 15.00% 13.40% 13.80% 13.10%
Reconciling Item, Corporate        
Segment Reporting [Line Items]        
ROE (2.50%) (2.50%) (2.90%) (2.80%)