v3.26.3
Investments - Cost and Fair Value, Net of Credit Loss Allowance, of Fixed Maturity Securities (Details) - USD ($)
$ in Thousands
Sep. 30, 2026
Dec. 31, 2025
Available-for-sale securities:    
Amortized cost $ 1,460,547  
Estimated fair value 1,411,389  
Held-to-maturity securities - states & political subdivisions    
Amortized cost 1,465,380 $ 1,368,061
Gross unrealized gains 1,525 17,455
Gross unrealized losses 51,255 15,825
Estimated fair value 1,415,650 1,369,691
Fair value of securities lent 56,400 64,500
Corporate debt securities    
Available-for-sale securities:    
Amortized cost 782,067 834,885
Gross unrealized gains 756 12,779
Gross unrealized losses 20,938 3,185
Estimated fair value 761,885 844,479
Collateralized debt obligations    
Available-for-sale securities:    
Amortized cost 243,583 133,224
Gross unrealized gains 198 207
Gross unrealized losses 505 164
Estimated fair value 243,276 133,267
Commercial mortgage-backed securities    
Available-for-sale securities:    
Amortized cost 160,749 139,516
Gross unrealized gains 497 2,808
Gross unrealized losses 5,016 1,783
Estimated fair value 156,230 140,541
Residential mortgage-backed securities    
Available-for-sale securities:    
Amortized cost 231,135 196,624
Gross unrealized gains 56 982
Gross unrealized losses 23,164 10,380
Estimated fair value 208,027 187,226
Other debt securities    
Available-for-sale securities:    
Amortized cost 42,120 34,863
Gross unrealized gains 18 543
Gross unrealized losses 1,007 254
Estimated fair value 41,131 35,152
U.S. Treasury    
Available-for-sale securities:    
Amortized cost 893 24,116
Gross unrealized gains 0 106
Gross unrealized losses 53 59
Estimated fair value 840 24,163
Total available-for-sale securities    
Available-for-sale securities:    
Amortized cost 1,460,547 1,363,228
Gross unrealized gains 1,525 17,425
Gross unrealized losses 50,683 15,825
Estimated fair value 1,411,389 1,364,828
Held-to-maturity securities - states & political subdivisions    
Fair value of securities lent 42,300 44,400
Held-to-maturity securities    
Held-to-maturity securities - states & political subdivisions    
Amortized cost 4,833 4,833
Gross unrealized gains 0 30
Gross unrealized losses 572 0
Estimated fair value $ 4,261 $ 4,863