v3.26.3
Investments - Schedule of Realized Gain and Loss and Investments in Unrealized Loss Position (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Dec. 31, 2025
Investments, Debt and Equity Securities [Abstract]          
Realized gross gains $ 3 $ 40 $ 677 $ 59  
Realized gross losses (199) (425) (1,131) (754)  
Impairments and changes in expected credit losses (1,430) $ (40) (1,430) $ (40)  
Fair Value          
Less than 12 months 3,288,239   3,288,239   $ 458,503
12 months or more 1,808,436   1,808,436   2,409,379
Total 5,096,675   5,096,675   2,867,882
Gross Unrealized Losses          
Less than 12 months (133,400)   (133,400)   (3,330)
12 months or more (289,447)   (289,447)   (209,963)
Total (422,847)   (422,847)   (213,293)
U.S. Treasury securities          
Fair Value          
Less than 12 months 250,695   250,695   1,048
12 months or more 67,149   67,149   179,121
Total 317,844   317,844   180,169
Gross Unrealized Losses          
Less than 12 months (4,748)   (4,748)   (8)
12 months or more (6,636)   (6,636)   (5,968)
Total (11,384)   (11,384)   (5,976)
U.S. agency mortgage-backed securities          
Fair Value          
Less than 12 months 651,356   651,356   45,415
12 months or more 469,704   469,704   638,729
Total 1,121,060   1,121,060   684,144
Gross Unrealized Losses          
Less than 12 months (32,901)   (32,901)   (90)
12 months or more (105,211)   (105,211)   (76,660)
Total (138,112)   (138,112)   (76,750)
Municipal debt securities          
Fair Value          
Less than 12 months 290,809   290,809   74,928
12 months or more 259,984   259,984   314,515
Total 550,793   550,793   389,443
Gross Unrealized Losses          
Less than 12 months (15,617)   (15,617)   (1,015)
12 months or more (51,446)   (51,446)   (35,210)
Total (67,063)   (67,063)   (36,225)
Non-U.S. government securities          
Fair Value          
Less than 12 months 0   0   0
12 months or more 42,169   42,169   56,024
Total 42,169   42,169   56,024
Gross Unrealized Losses          
Less than 12 months 0   0   0
12 months or more (11,256)   (11,256)   (8,446)
Total (11,256)   (11,256)   (8,446)
Corporate debt securities:          
Fair Value          
Less than 12 months 1,346,480   1,346,480   196,571
12 months or more 553,944   553,944   706,561
Total 1,900,424   1,900,424   903,132
Gross Unrealized Losses          
Less than 12 months (64,970)   (64,970)   (1,106)
12 months or more (78,047)   (78,047)   (53,441)
Total (143,017)   (143,017)   (54,547)
Residential and commercial mortgage securities          
Fair Value          
Less than 12 months 135,269   135,269   36,552
12 months or more 302,704   302,704   364,271
Total 437,973   437,973   400,823
Gross Unrealized Losses          
Less than 12 months (5,104)   (5,104)   (240)
12 months or more (24,932)   (24,932)   (23,142)
Total (30,036)   (30,036)   (23,382)
Asset-backed securities          
Fair Value          
Less than 12 months 575,498   575,498   103,989
12 months or more 112,782   112,782   150,158
Total 688,280   688,280   254,147
Gross Unrealized Losses          
Less than 12 months (10,052)   (10,052)   (871)
12 months or more (11,919)   (11,919)   (7,096)
Total (21,971)   (21,971)   $ (7,967)
Money market funds          
Fair Value          
Less than 12 months 38,132   38,132    
12 months or more 0   0    
Total 38,132   38,132    
Gross Unrealized Losses          
Less than 12 months (8)   (8)    
12 months or more 0   0    
Total $ (8)   $ (8)