v3.24.3
Investments (Available-For-Sale Securities by Contractual Maturity) (Details) - USD ($)
$ in Thousands
Sep. 30, 2024
Dec. 31, 2023
Debt Securities, Available-for-Sale [Line Items]    
Amortized Cost $ 3,849,715 $ 3,758,720
Total Fair Value 3,686,132 3,493,597
U.S. Treasury obligations    
Debt Securities, Available-for-Sale [Line Items]    
Amortized Cost 261,442 259,834
Due in one year or less 36,542  
Due after one year through five years 181,615  
Due after five years through ten years 30,406  
Due after ten years 2,738  
Total Fair Value 251,301 243,525
U.S. Government-sponsored enterprise obligations    
Debt Securities, Available-for-Sale [Line Items]    
Amortized Cost 16,575 19,752
Due in one year or less 6,471  
Due after one year through five years 7,016  
Due after five years through ten years 523  
Due after ten years 2,014  
Total Fair Value 16,024 18,724
State and municipal bonds    
Debt Securities, Available-for-Sale [Line Items]    
Amortized Cost 482,509 482,367
Due in one year or less 39,434  
Due after one year through five years 154,088  
Due after five years through ten years 155,687  
Due after ten years 118,570  
Total Fair Value 467,779 454,381
Corporate debt    
Debt Securities, Available-for-Sale [Line Items]    
Amortized Cost 1,850,831 1,883,308
Due in one year or less 176,203  
Due after one year through five years 911,876  
Due after five years through ten years 573,680  
Due after ten years 108,661  
Total Fair Value 1,770,420 1,750,574
Residential mortgage-backed securities    
Debt Securities, Available-for-Sale [Line Items]    
Amortized Cost 534,605 481,267
Total Fair Value 494,095 430,137
Agency commercial mortgage-backed securities    
Debt Securities, Available-for-Sale [Line Items]    
Amortized Cost 8,022 9,369
Total Fair Value 7,251 8,387
Other commercial mortgage-backed securities    
Debt Securities, Available-for-Sale [Line Items]    
Amortized Cost 212,274 210,469
Total Fair Value 200,389 189,474
Other asset-backed securities    
Debt Securities, Available-for-Sale [Line Items]    
Amortized Cost 483,457 412,354
Total Fair Value $ 478,873 $ 398,395