v3.26.3
Investments - Schedule of Available-For-Sale Securities Disclosure (Details) - USD ($)
$ in Thousands
Sep. 30, 2026
Jun. 30, 2026
Dec. 31, 2025
Sep. 30, 2025
Jun. 30, 2025
Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]            
Cost/ Amortized Cost $ 10,382,993   $ 9,576,878      
Allowance for Credit Losses (51,561) $ (39,102) (31,287) $ (29,076) $ (28,733) $ (31,948)
Unrealized Gains 25,053   133,703      
Unrealized Losses (546,427)   (222,118)      
Fair Value 9,810,058   9,457,176      
U.S. government and government agencies            
Debt Securities, Available-for-sale [Line Items]            
Cost/ Amortized Cost 207,774   177,877      
Allowance for Credit Losses 0   0      
Unrealized Gains 0   108      
Unrealized Losses (25,658)   (14,778)      
Fair Value 182,116   163,207      
Foreign government            
Debt Securities, Available-for-sale [Line Items]            
Cost/ Amortized Cost 17,109   10,768      
Allowance for Credit Losses (75) (79) (16) (19) (21) (21)
Unrealized Gains 8   47      
Unrealized Losses (1,679)   (797)      
Fair Value 15,363   10,002      
Obligations of states and political subdivisions            
Debt Securities, Available-for-sale [Line Items]            
Cost/ Amortized Cost 540,579   567,757      
Allowance for Credit Losses (619) (305) (259) (326) (390) (570)
Unrealized Gains 162   6,342      
Unrealized Losses (48,207)   (23,883)      
Fair Value 491,915   549,957      
Corporate securities            
Debt Securities, Available-for-sale [Line Items]            
Cost/ Amortized Cost 3,959,528   3,409,875      
Allowance for Credit Losses (24,893) (12,398) (7,691) (8,020) (9,571) (14,924)
Unrealized Gains 8,882   73,842      
Unrealized Losses (189,692)   (71,862)      
Fair Value 3,753,825   3,404,164      
Collateralized loan obligations (“CLO”) and other asset-backed securities (“ABS”)            
Debt Securities, Available-for-sale [Line Items]            
Cost/ Amortized Cost 2,576,294   2,570,451      
Allowance for Credit Losses (14,417) (14,917) (11,902) (9,234) (7,230) (4,889)
Unrealized Gains 14,427   26,596      
Unrealized Losses (70,902)   (34,859)      
Fair Value 2,505,402   2,550,286      
Residential mortgage-backed securities (“RMBS”)            
Debt Securities, Available-for-sale [Line Items]            
Cost/ Amortized Cost 2,447,862   2,127,004      
Allowance for Credit Losses (11,543) (11,394) (11,284) (11,368) (11,422) (11,544)
Unrealized Gains 1,345   21,547      
Unrealized Losses (184,471)   (61,334)      
Fair Value 2,253,193   2,075,933      
Commercial mortgage-backed securities (“CMBS”)            
Debt Securities, Available-for-sale [Line Items]            
Cost/ Amortized Cost 633,847   713,146      
Allowance for Credit Losses (14) $ (9) (135) $ (109) $ (99) $ 0
Unrealized Gains 229   5,221      
Unrealized Losses (25,818)   (14,605)      
Fair Value $ 608,244   $ 703,627