Fair Value - Fair Value Measurements on a Recurring Basis by Asset Class and Level of Input (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	$ 1,364,828
Total	1,455,591	$ 1,129,506
Fair value of securities lent	64,500
Total available-for-sale securities
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	1,364,828	1,043,615
Fair value of securities lent	44,400
Corporate debt securities
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	844,479	643,943
Fair value of securities lent		7,300
Collateralized debt obligations
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	133,267	114,127
Commercial mortgage-backed securities
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	140,541	124,982
Residential mortgage-backed securities
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	187,226	133,812
Other debt securities
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	35,152	26,751
U.S. Treasury
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	24,163
Equity securities
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	90,763	85,891
Fair value of securities lent	20,100
Equity securities | Financial services sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	74,614	69,930
Equity securities | Utilities sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	3,696	5,629
Equity securities | Energy sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	2,713	4,117
Equity securities | Consumer sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	5,563	3,341
Equity securities | Technology sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	3,224	1,974
Equity securities | Communications sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	953	900
Level 1
Fair value measurements on a recurring basis by asset class and level of input
Total	3,591	1,106
Level 1 | Total available-for-sale securities
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	998	0
Level 1 | Corporate debt securities
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	998	0
Level 1 | Collateralized debt obligations
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	0	0
Level 1 | Commercial mortgage-backed securities
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	0	0
Level 1 | Residential mortgage-backed securities
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	0	0
Level 1 | Other debt securities
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	0	0
Level 1 | U.S. Treasury
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	0
Level 1 | Equity securities
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	2,593	1,106
Level 1 | Equity securities | Financial services sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	2,593	1,052
Level 1 | Equity securities | Utilities sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	0	0
Level 1 | Equity securities | Energy sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	0	0
Level 1 | Equity securities | Consumer sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	0	54
Level 1 | Equity securities | Technology sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	0	0
Level 1 | Equity securities | Communications sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	0	0
Level 2
Fair value measurements on a recurring basis by asset class and level of input
Total	1,412,181	1,091,069
Level 2 | Total available-for-sale securities
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	1,336,076	1,013,258
Level 2 | Corporate debt securities
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	839,542	637,675
Level 2 | Collateralized debt obligations
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	133,267	114,127
Level 2 | Commercial mortgage-backed securities
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	117,520	100,893
Level 2 | Residential mortgage-backed securities
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	186,432	133,812
Level 2 | Other debt securities
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	35,152	26,751
Level 2 | U.S. Treasury
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	24,163
Level 2 | Equity securities
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	76,105	77,811
Level 2 | Equity securities | Financial services sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	66,350	65,378
Level 2 | Equity securities | Utilities sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	3,696	5,629
Level 2 | Equity securities | Energy sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	2,713	4,117
Level 2 | Equity securities | Consumer sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	2,393	1,787
Level 2 | Equity securities | Technology sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	0	0
Level 2 | Equity securities | Communications sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	953	900
Level 3
Fair value measurements on a recurring basis by asset class and level of input
Total	39,819	37,331
Level 3 | Total available-for-sale securities
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	27,754	30,357
Level 3 | Corporate debt securities
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	3,939	6,268
Level 3 | Collateralized debt obligations
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	0	0
Level 3 | Commercial mortgage-backed securities
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	23,021	24,089
Level 3 | Residential mortgage-backed securities
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	794	0
Level 3 | Other debt securities
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	0	0
Level 3 | U.S. Treasury
Fair value measurements on a recurring basis by asset class and level of input
Total available-for-sale securities	0
Level 3 | Equity securities
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	12,065	6,974
Level 3 | Equity securities | Financial services sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	5,671	3,500
Level 3 | Equity securities | Utilities sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	0	0
Level 3 | Equity securities | Energy sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	0	0
Level 3 | Equity securities | Consumer sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	3,170	1,500
Level 3 | Equity securities | Technology sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	3,224	1,974
Level 3 | Equity securities | Communications sector
Fair value measurements on a recurring basis by asset class and level of input
Total equity securities	$ 0	$ 0