Investment Securities - Amortized cost and estimated fair value (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Carrying Value
Due within one year or less	$ 5,981
Due after one year through five years	51,009
Due after five years through ten years	60,325
Due after 10 years	12,773
Held-to-maturity securities carrying value	130,088
Amortized Cost	303,486	$ 321,902
Estimated Fair Value
Due within one year or less	5,875
Due after one year through five years	45,878
Due after five years through ten years	49,427
Due after 10 years	10,257
Total investment securities	111,437
Debt Securities, Held-to-maturity, Fair Value, Total	248,239	270,912
Amortized Cost
Due after one year through five years	17,119
Due after five years through ten years	80,670
Due after 10 years	41,392
Total investment securities available-for-sale	139,181
Total investment securities, Amortized Cost	796,026
Fair Value
Due after one year through five years	15,706
Due after five years through ten years	66,779
Due after 10 years	35,893
Total investment securities available-for-sale	118,378
Debt Securities, Available-for-sale, Total	640,001	717,324
Mortgage backed securities - Residential agency
Carrying Value
Mortgage-backed securities, Carrying value	173,398
Amortized Cost	173,398	184,115
Estimated Fair Value
Mortgage-backed securities, Fair value	136,802
Debt Securities, Held-to-maturity, Fair Value, Total	136,802	150,861
Amortized Cost
Mortgage-backed securities, Amortized Cost	656,845
Fair Value
Mortgage-backed securities, Fair value	521,623
Debt Securities, Available-for-sale, Total	$ 521,623	$ 587,679