Investments - Investments by contractual maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Schedule of Available-for-sale Securities
Within one year, amortized cost	$ 0	$ 0
Within one year, estimated fair value	0	0
After one year through five years, amortized cost	15,662	9,992
After one year through five years, estimated fair value	13,754	8,954
After five years through ten years, amortized cost	34,482	40,264
After five years through ten years, estimated fair value	30,340	35,379
After ten years, amortized cost	157,157	157,804
After ten years, estimated fair value	143,189	144,843
Total securities with single maturity date, amortized cost	207,301	208,060
Total securities with single maturity date, estimated fair value	187,283	189,176
Debt securities, amortized cost	643,525	669,646
Debt Securities, Available-for-sale	573,534	597,196
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Fair Value	0	0
Debt Securities, Held-to-Maturity, Fair Value, Maturity, Allocated and Single Maturity Date, Year One	0	0
Debt Securities, Held-to-Maturity, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five	8,142	8,136
Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Maturity, Allocated and Single Maturity Date, after Year One through Five	8,492	8,463
Debt Securities, Held-to-maturity, Maturity, Rolling after Five Through Ten Years, Weighted Average Yield	74,868	74,746
Debt Securities, Held-to-Maturity, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10	68,489	68,552
Debt Securities, Held-to-Maturity, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 10	99,574	101,264
Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Maturity, Allocated and Single Maturity Date, after Year 10	108,739	108,861
Held-to-maturity investment securities	192,099	192,070
Held-to-maturity debt securities, at amortized cost less allowance for credit losses of $894 at March 31, 2024 and $1,051 at December 31, 2023	176,205	177,952
Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Maturity, without Single Maturity Date	303,406	303,493
Debt Securities, Held-to-maturity, Maturity, without Single Maturity Date, Fair Value	274,893	277,003
U.S. Government agencies
Schedule of Available-for-sale Securities
Investment securities not due at a single maturity date, amortized cost	100	102
Investment securities not due at a single maturity date, estimated fair value	92	95
Debt securities, amortized cost	100	102
Debt Securities, Available-for-sale	92	95
U.S. Government sponsored entities and agencies collateralized by residential mortgage obligations
Schedule of Available-for-sale Securities
Investment securities not due at a single maturity date, amortized cost	86,205	88,874
Investment securities not due at a single maturity date, estimated fair value	80,798	83,352
Debt securities, amortized cost	86,205	88,874
Debt Securities, Available-for-sale	80,798	83,352
Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Maturity, without Single Maturity Date	10,841	10,758
Debt Securities, Held-to-maturity, Maturity, without Single Maturity Date, Fair Value	8,831	9,066
Private label mortgage and asset backed securities
Schedule of Available-for-sale Securities
Investment securities not due at a single maturity date, amortized cost	349,919	372,610
Investment securities not due at a single maturity date, estimated fair value	305,361	324,573
Debt securities, amortized cost	349,919	372,610
Debt Securities, Available-for-sale	305,361	324,573
Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Maturity, without Single Maturity Date	54,354	54,579
Debt Securities, Held-to-maturity, Maturity, without Single Maturity Date, Fair Value	48,616	48,635
Corporate debt securities
Schedule of Available-for-sale Securities
Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Maturity, without Single Maturity Date	46,112	46,086
Debt Securities, Held-to-maturity, Maturity, without Single Maturity Date, Fair Value	$ 41,241	$ 41,350