v3.26.3
Investments - Schedule of Realized and Unrealized Gains (Losses) on Investments and Net Investment Income (Loss) (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Net realized and unrealized gains (losses) on investments:        
Net realized gains (losses) on investments $ 166,722 $ 109,355 $ 554,472 $ 424,142
Change in net unrealized gains (losses) on investments 41,804 5,781 32,986 147,822
Net realized and unrealized gains (losses) on investments 208,526 115,136 587,458 571,964
Net investment income (loss):        
Interest and other 43,358 36,879 124,638 104,151
Management fees (16,432) (13,889) (46,544) (40,574)
Other expenses (311) (263) (1,010) (856)
Net investment income (loss) 26,615 22,727 77,084 62,721
Total net realized and unrealized gains (losses) on investments and net investment income (loss) 235,141 137,863 664,542 634,685
Total fixed maturities        
Net investment income (loss):        
Interest and other 36,065 30,070 104,850 82,674
Short-term investments        
Net investment income (loss):        
Interest and other 3 155 22 453
TS Hamilton Fund        
Net realized and unrealized gains (losses) on investments:        
Net realized gains (losses) on investments 173,705 106,081 563,788 420,002
Change in net unrealized gains (losses) on investments 132,116 (1,446) 170,469 77,326
Net investment income (loss):        
Interest and other 1,507 3,243 5,091 7,837
Cash and cash equivalents        
Net investment income (loss):        
Interest and other 5,002 3,986 13,491 12,576
Other        
Net investment income (loss):        
Interest and other 781 (575) 1,184 611
Fixed maturities and short-term investments        
Net realized and unrealized gains (losses) on investments:        
Net realized gains (losses) on investments (6,983) 3,274 (9,316) 4,140
Change in net unrealized gains (losses) on investments $ (90,312) $ 7,227 $ (137,483) $ 70,496