v3.25.2
Segment Information - Summary of Operating Results by Segment (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Segment Reporting Information [Line Items]        
Net premiums earned $ 1,366,738 $ 1,236,024 $ 2,649,808 $ 2,402,703
Total incurred losses and loss adjustment expenses     2,160,850 1,840,679
Policy acquisition costs 227,880 203,682 456,601 399,722
Other operating expenses 96,025 81,702 175,478 158,790
Net investment income 78,759 68,970 160,238 133,989
Net realized investment gains 23,480 2,899 46,801 41,090
Other income (loss) 8,908 (2,899) 14,916 1,298
Interest expense (7,195) (7,799) (14,383) (15,572)
Income before income taxes 206,748 75,097 64,451 164,317
Net income 166,472 62,568 58,145 136,030
Operating Segments        
Segment Reporting Information [Line Items]        
Net premiums earned 1,366,700 1,236,000 2,649,800 2,402,700
Losses 797,200 800,800 1,866,600 1,586,600
Loss adjustment expenses 142,800 135,900 294,300 254,100
Total incurred losses and loss adjustment expenses 940,000 936,700 2,160,900 1,840,700
Policy acquisition costs 227,900 203,700 456,600 399,700
Other operating expenses 96,000 81,700 175,500 158,800
Underwriting gain (loss) 102,800 13,900 (143,200) 3,500
Net investment income 78,800 69,000 160,200 134,000
Net realized investment gains 23,500 2,900 46,800 41,100
Other income (loss) 8,800 (2,900) 15,000 1,300
Interest expense (7,200) (7,800) (14,300) (15,600)
Income before income taxes 206,700 75,100 64,500 164,300
Net income 166,500 62,600 58,100 136,000
Property & Casualty        
Segment Reporting Information [Line Items]        
Net premiums earned 1,359,342 1,228,696 2,635,100 2,388,065
Property & Casualty | Operating Segments        
Segment Reporting Information [Line Items]        
Net premiums earned 1,359,300 1,228,700 2,635,100 2,388,100
Losses 793,300 796,900 1,859,000 1,579,100
Loss adjustment expenses 142,300 135,500 293,300 253,300
Total incurred losses and loss adjustment expenses 935,600 932,400 2,152,300 1,832,400
Policy acquisition costs 225,000 200,800 450,800 393,900
Other operating expenses 95,200 81,200 174,100 157,400
Underwriting gain (loss) 103,500 14,300 (142,100) 4,400
Other | Operating Segments        
Segment Reporting Information [Line Items]        
Net premiums earned 7,400 7,300 14,700 14,600
Losses 3,900 3,900 7,600 7,500
Loss adjustment expenses 500 400 1,000 800
Total incurred losses and loss adjustment expenses 4,400 4,300 8,600 8,300
Policy acquisition costs 2,900 2,900 5,800 5,800
Other operating expenses 800 500 1,400 1,400
Underwriting gain (loss) $ (700) $ (400) $ (1,100) $ (900)