v3.26.1
Investments (Schedule of Available-For-Sale Fixed Maturities) (Details) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Mar. 31, 2025
Dec. 31, 2024
Debt Securities, Available-for-Sale [Line Items]        
Amortized Cost $ 3,775,708 $ 3,793,777    
Allowance for Expected Credit Losses 4,299 4,306 $ 3,656 $ 3,399
Gross Unrealized Gains 17,452 30,060    
Gross Unrealized Losses 145,648 133,744    
Estimated Fair Value 3,643,213 3,685,787    
U.S. Treasury obligations        
Debt Securities, Available-for-Sale [Line Items]        
Amortized Cost 187,671 224,114    
Allowance for Expected Credit Losses 0 0    
Gross Unrealized Gains 490 871    
Gross Unrealized Losses 5,759 5,583    
Estimated Fair Value 182,402 219,402    
U.S. Government-sponsored enterprise obligations        
Debt Securities, Available-for-Sale [Line Items]        
Amortized Cost 9,131 10,124    
Allowance for Expected Credit Losses 0 0    
Gross Unrealized Gains 2 9    
Gross Unrealized Losses 287 281    
Estimated Fair Value 8,846 9,852    
State and municipal bonds        
Debt Securities, Available-for-Sale [Line Items]        
Amortized Cost 447,641 439,082    
Allowance for Expected Credit Losses 0 0    
Gross Unrealized Gains 3,739 4,297    
Gross Unrealized Losses 13,648 13,316    
Estimated Fair Value 437,732 430,063    
Corporate debt        
Debt Securities, Available-for-Sale [Line Items]        
Amortized Cost 1,805,088 1,807,392    
Allowance for Expected Credit Losses 3,767 3,767 3,125 2,608
Gross Unrealized Gains 6,999 14,932    
Gross Unrealized Losses 64,998 57,043    
Estimated Fair Value 1,743,322 1,761,514    
Residential mortgage-backed securities        
Debt Securities, Available-for-Sale [Line Items]        
Amortized Cost 634,414 629,348    
Allowance for Expected Credit Losses 204 210 $ 192 $ 197
Gross Unrealized Gains 3,678 5,659    
Gross Unrealized Losses 45,269 42,956    
Estimated Fair Value 592,619 591,841    
Agency commercial mortgage-backed securities        
Debt Securities, Available-for-Sale [Line Items]        
Amortized Cost 5,920 6,062    
Allowance for Expected Credit Losses 0 0    
Gross Unrealized Gains 6 10    
Gross Unrealized Losses 721 712    
Estimated Fair Value 5,205 5,360    
Other commercial mortgage-backed securities        
Debt Securities, Available-for-Sale [Line Items]        
Amortized Cost 224,308 214,535    
Allowance for Expected Credit Losses 62 62    
Gross Unrealized Gains 486 851    
Gross Unrealized Losses 7,487 7,203    
Estimated Fair Value 217,245 208,121    
Other asset-backed securities        
Debt Securities, Available-for-Sale [Line Items]        
Amortized Cost 461,535 463,120    
Allowance for Expected Credit Losses 266 267    
Gross Unrealized Gains 2,052 3,431    
Gross Unrealized Losses 7,479 6,650    
Estimated Fair Value $ 455,842 $ 459,634