v3.25.2
Investments - Summary of Fixed Maturity Securities Classified as Available-for-Sale (Details) - USD ($)
$ in Thousands
Jun. 30, 2025
Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]    
Amortized cost $ 6,012,143 $ 5,876,502
Gross unrealized gains 59,562 20,711
Gross unrealized losses (174,887) (272,440)
Fair value 5,896,818 5,624,773
Total investments    
Debt Securities, Available-for-sale [Line Items]    
Amortized cost 6,015,141 5,879,872
Gross unrealized gains 59,565 20,712
Gross unrealized losses (174,887) (272,444)
Fair value 5,899,819 5,628,140
U.S. government, agencies and GSEs    
Debt Securities, Available-for-sale [Line Items]    
Amortized cost 263,827 281,858
Gross unrealized gains 3,020 590
Gross unrealized losses (1,866) (5,085)
Fair value 264,981 277,363
State and political subdivisions    
Debt Securities, Available-for-sale [Line Items]    
Amortized cost 538,822 541,715
Gross unrealized gains 1,628 1,388
Gross unrealized losses (61,095) (75,627)
Fair value 479,355 467,476
Non-U.S. government    
Debt Securities, Available-for-sale [Line Items]    
Amortized cost 152,936 85,566
Gross unrealized gains 2,215 94
Gross unrealized losses (615) (1,858)
Fair value 154,536 83,802
U.S. corporate    
Debt Securities, Available-for-sale [Line Items]    
Amortized cost 2,891,693 2,943,900
Gross unrealized gains 34,023 11,363
Gross unrealized losses (74,241) (129,584)
Fair value 2,851,475 2,825,679
Non-U.S. corporate    
Debt Securities, Available-for-sale [Line Items]    
Amortized cost 789,886 800,141
Gross unrealized gains 9,931 2,533
Gross unrealized losses (16,633) (30,050)
Fair value 783,184 772,624
Residential mortgage-backed    
Debt Securities, Available-for-sale [Line Items]    
Amortized cost 260,372 8,394
Gross unrealized gains 1,602 27
Gross unrealized losses (559) (57)
Fair value 261,415 8,364
Other asset-backed    
Debt Securities, Available-for-sale [Line Items]    
Amortized cost 1,066,383 1,214,928
Gross unrealized gains 6,555 4,716
Gross unrealized losses (19,875) (30,179)
Fair value 1,053,063 1,189,465
Short-term investments    
Debt Securities, Available-for-sale [Line Items]    
Amortized cost 2,998 3,370
Gross unrealized gains 3 1
Gross unrealized losses 0 (4)
Fair value 3,001 $ 3,367
Commercial mortgage-backed    
Debt Securities, Available-for-sale [Line Items]    
Amortized cost 48,224  
Gross unrealized gains 588  
Gross unrealized losses (3)  
Fair value $ 48,809