v3.26.1
Investments - Schedule of Fixed Maturity and Short-Term Investments (Details) - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Debt Securities, Available-for-Sale [Line Items]    
Amortized Cost $ 3,489,236 $ 3,410,992
Gross Unrealized Gains 14,577 45,265
Gross Unrealized Losses (33,306) (17,255)
Investments, at fair value 3,470,507 3,439,002
Total fixed maturities    
Debt Securities, Available-for-Sale [Line Items]    
Amortized Cost 3,133,507 3,210,940
Gross Unrealized Gains 13,797 44,846
Gross Unrealized Losses (33,250) (17,243)
Investments, at fair value 3,114,054 3,238,543
U.S. government treasuries    
Debt Securities, Available-for-Sale [Line Items]    
Amortized Cost 642,619 795,780
Gross Unrealized Gains 162 4,782
Gross Unrealized Losses (6,806) (2,728)
Investments, at fair value 635,975 797,834
U.S. states, territories and municipalities    
Debt Securities, Available-for-Sale [Line Items]    
Amortized Cost 10,706 12,924
Gross Unrealized Gains 13 89
Gross Unrealized Losses (118) (53)
Investments, at fair value 10,601 12,960
Non-U.S. sovereign governments and supranationals    
Debt Securities, Available-for-Sale [Line Items]    
Amortized Cost 110,285 108,296
Gross Unrealized Gains 962 3,102
Gross Unrealized Losses (2,463) (537)
Investments, at fair value 108,784 110,861
Corporate    
Debt Securities, Available-for-Sale [Line Items]    
Amortized Cost 1,737,396 1,557,582
Gross Unrealized Gains 10,459 29,899
Gross Unrealized Losses (15,577) (3,337)
Investments, at fair value 1,732,278 1,584,144
Residential mortgage-backed securities - Agency    
Debt Securities, Available-for-Sale [Line Items]    
Amortized Cost 221,454 370,516
Gross Unrealized Gains 1,403 4,419
Gross Unrealized Losses (5,243) (9,285)
Investments, at fair value 217,614 365,650
Residential mortgage-backed securities - Non-agency    
Debt Securities, Available-for-Sale [Line Items]    
Amortized Cost 58,086 33,052
Gross Unrealized Gains 156 319
Gross Unrealized Losses (1,520) (826)
Investments, at fair value 56,722 32,545
Commercial mortgage-backed securities - Non-agency    
Debt Securities, Available-for-Sale [Line Items]    
Amortized Cost 78,767 94,223
Gross Unrealized Gains 209 835
Gross Unrealized Losses (586) (360)
Investments, at fair value 78,390 94,698
Other asset-backed securities    
Debt Securities, Available-for-Sale [Line Items]    
Amortized Cost 274,194 238,567
Gross Unrealized Gains 433 1,401
Gross Unrealized Losses (937) (117)
Investments, at fair value 273,690 239,851
Short-term investments    
Debt Securities, Available-for-Sale [Line Items]    
Amortized Cost 355,729 200,052
Gross Unrealized Gains 780 419
Gross Unrealized Losses (56) (12)
Investments, at fair value $ 356,453 $ 200,459