Investments - Investments Classified by Contractual Maturity Date (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Available for sale, Amortized Cost
Due in one year or less	$ 145,257
Due after one year through five years	220,941
Due after five years through ten years	238,026
Due after ten years	294,606
Agency mortgage-backed securities	1,237,422
Amortized Cost	2,136,252	$ 2,025,483
Available for sale, Estimated Fair Value
Due in one year or less	144,058
Due after one year through five years	212,587
Due after five years through ten years	202,822
Due after ten years	238,312
Agency mortgage-backed securities	1,192,289
Fair Value	1,990,068	1,862,270
Held to maturity, Amortized Cost
Due in one year or less	7,231
Due after one year through five years	125,753
Due after five years through ten years	218,879
Due after ten years	635,738
Agency mortgage-backed securities	46,976
Amortized Cost	1,034,577	929,192
Held to maturity, Estimated Fair Value
Due in one year or less	7,214
Due after one year through five years	119,955
Due after five years through ten years	213,168
Due after ten years	577,256
Agency mortgage-backed securities	42,756
Total securities held-to-maturity	$ 960,349	$ 858,871