Loans - Risk by loan portfolio (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 2,174,457		$ 2,172,063
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Total Loans	2,174,457		2,172,063
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Total loans	445	$ 233
SBA loans held for investment
Financing Receivable, Recorded Investment [Line Items]
Total loans	39,009		38,584
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Year	964		1,938
One Year Prior to Current Year	1,878		8,360
Two Years Prior to Current Year	8,333		7,265
Three Years Prior to Current Year	7,385		6,783
Four Years Prior to Current Year	6,464		2,634
Five Years Prior to Current Year and Earlier	13,985		11,604
Total Loans	39,009		38,584
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
One Year Prior to Current Year			100
Four Years Prior to Current Year			113
Total loans		113	213
SBA PPP loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,168		2,318
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Two Years Prior to Current Year			2,318
Three Years Prior to Current Year	2,168
Total Loans	2,168		2,318
Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,291,319		1,277,460
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Year	14,828		139,622
One Year Prior to Current Year	152,337		343,755
Two Years Prior to Current Year	336,777		183,293
Three Years Prior to Current Year	182,494		128,179
Four Years Prior to Current Year	126,854		103,132
Five Years Prior to Current Year and Earlier	374,342		282,096
Revolving Loans Amortized Cost Basis	103,687		97,383
Total Loans	1,291,319		1,277,460
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Two Years Prior to Current Year			150
Four Years Prior to Current Year			350
Five Years Prior to Current Year and Earlier	98		252
Total loans	98		752
Commercial loans | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	977,437		986,230
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Total Loans	977,437		986,230
Commercial loans | Commercial real estate construction
Financing Receivable, Recorded Investment [Line Items]
Total loans	142,345		129,159
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Total Loans	142,345		129,159
Commercial loans | Commercial & industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans	133,409		128,402
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Total Loans	133,409		128,402
Residential mortgage loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	627,464		631,506
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Year	23,064		102,892
One Year Prior to Current Year	85,980		256,883
Two Years Prior to Current Year	251,088		75,300
Three Years Prior to Current Year	72,505		53,053
Four Years Prior to Current Year	49,092		31,427
Five Years Prior to Current Year and Earlier	145,735		111,951
Total Loans	627,464		631,506
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Two Years Prior to Current Year			25
Five Years Prior to Current Year and Earlier			68
Total loans			93
Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	72,275		72,676
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Year	693		3,428
One Year Prior to Current Year	2,973		4,777
Two Years Prior to Current Year	4,400		3,681
Three Years Prior to Current Year	3,035		795
Four Years Prior to Current Year	753		2,481
Five Years Prior to Current Year and Earlier	11,256		7,763
Revolving Loans Amortized Cost Basis	49,165		49,751
Total Loans	72,275		72,676
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
One Year Prior to Current Year			26
Two Years Prior to Current Year	21		552
Three Years Prior to Current Year	49
Total loans	70	$ 120	578
Consumer loans | Home equity [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	67,448		67,037
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Total Loans	67,448		67,037
Consumer loans | Consumer other
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,827		5,639
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Total Loans	4,827		5,639
Residential construction loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	123,783		131,277
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Year	6,595		28,827
One Year Prior to Current Year	34,782		72,257
Two Years Prior to Current Year	64,368		25,395
Three Years Prior to Current Year	15,091		1,965
Four Years Prior to Current Year	1,965		491
Five Years Prior to Current Year and Earlier	982		2,342
Total Loans	123,783		131,277
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Five Years Prior to Current Year and Earlier	277		600
Revolving Loans Amortized Cost Basis			400
Total loans	277		1,000
Total loans held for investment including PPP
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,156,018		2,153,821
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Year	46,144		276,707
One Year Prior to Current Year	277,950		686,032
Two Years Prior to Current Year	664,966		297,252
Three Years Prior to Current Year	282,678		190,775
Four Years Prior to Current Year	185,128		140,165
Five Years Prior to Current Year and Earlier	546,300		415,756
Revolving Loans Amortized Cost Basis	152,852		147,134
Total Loans	2,156,018		2,153,821
Performing | Residential mortgage loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	620,024		621,180
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Year	23,064		102,892
One Year Prior to Current Year	85,980		253,919
Two Years Prior to Current Year	249,423		72,586
Three Years Prior to Current Year	70,123		51,999
Four Years Prior to Current Year	48,833		30,482
Five Years Prior to Current Year and Earlier	142,601		109,302
Total Loans	620,024		621,180
Performing | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	71,908		72,295
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Year	693		3,428
One Year Prior to Current Year	2,973		4,777
Two Years Prior to Current Year	4,400		3,681
Three Years Prior to Current Year	3,035		670
Four Years Prior to Current Year	644		2,481
Five Years Prior to Current Year and Earlier	11,255		7,507
Revolving Loans Amortized Cost Basis	48,908		49,751
Total Loans	71,908		72,295
Performing | Residential construction loans
Financing Receivable, Recorded Investment [Line Items]
Total loans			129,136
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Year			28,827
One Year Prior to Current Year			72,257
Two Years Prior to Current Year			25,395
Three Years Prior to Current Year			1,418
Four Years Prior to Current Year			491
Five Years Prior to Current Year and Earlier			748
Total Loans			129,136
Nonperforming | Residential mortgage loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,440		10,326
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
One Year Prior to Current Year			2,964
Two Years Prior to Current Year	1,665		2,714
Three Years Prior to Current Year	2,382		1,054
Four Years Prior to Current Year	259		945
Five Years Prior to Current Year and Earlier	3,134		2,649
Total Loans	7,440		10,326
Nonperforming | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	367		381
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Three Years Prior to Current Year			125
Four Years Prior to Current Year	109
Five Years Prior to Current Year and Earlier	1		256
Revolving Loans Amortized Cost Basis	257
Total Loans	367		381
Nonperforming | Residential construction loans
Financing Receivable, Recorded Investment [Line Items]
Total loans			2,141
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Three Years Prior to Current Year			547
Five Years Prior to Current Year and Earlier			1,594
Total Loans			2,141
Pass | SBA loans held for investment
Financing Receivable, Recorded Investment [Line Items]
Total loans	31,944		31,713
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Year	964		1,938
One Year Prior to Current Year	1,878		5,339
Two Years Prior to Current Year	5,241		4,723
Three Years Prior to Current Year	4,843		6,083
Four Years Prior to Current Year	5,778		2,634
Five Years Prior to Current Year and Earlier	13,240		10,996
Total Loans	31,944		31,713
Pass | SBA PPP loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,168		2,318
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Two Years Prior to Current Year			2,318
Three Years Prior to Current Year	2,168
Total Loans	2,168		2,318
Pass | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,279,567		1,262,692
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Year	14,828		139,622
One Year Prior to Current Year	152,337		343,755
Two Years Prior to Current Year	336,287		181,419
Three Years Prior to Current Year	180,893		128,165
Four Years Prior to Current Year	126,845		101,274
Five Years Prior to Current Year and Earlier	365,085		271,469
Revolving Loans Amortized Cost Basis	103,292		96,988
Total Loans	1,279,567		1,262,692
Pass | Residential construction loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	119,674
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Year	6,595
One Year Prior to Current Year	34,782
Two Years Prior to Current Year	64,368
Three Years Prior to Current Year	12,511
Four Years Prior to Current Year	1,418
Total Loans	119,674
Special mention | SBA loans held for investment
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,872		2,662
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
One Year Prior to Current Year			1,765
Two Years Prior to Current Year	1,836		356
Three Years Prior to Current Year	356		510
Four Years Prior to Current Year	510
Five Years Prior to Current Year and Earlier	170		31
Total Loans	2,872		2,662
Special mention | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	8,780		11,203
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Two Years Prior to Current Year	490		1,815
Three Years Prior to Current Year	1,464
Four Years Prior to Current Year			1,570
Five Years Prior to Current Year and Earlier	6,431		7,423
Revolving Loans Amortized Cost Basis	395		395
Total Loans	8,780		11,203
Substandard | SBA loans held for investment
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,193		4,209
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
One Year Prior to Current Year			1,256
Two Years Prior to Current Year	1,256		2,186
Three Years Prior to Current Year	2,186		190
Four Years Prior to Current Year	176
Five Years Prior to Current Year and Earlier	575		577
Total Loans	4,193		4,209
Substandard | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,972		3,565
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Two Years Prior to Current Year			59
Three Years Prior to Current Year	137		14
Four Years Prior to Current Year	9		288
Five Years Prior to Current Year and Earlier	2,826		3,204
Total Loans	2,972		$ 3,565
Substandard | Residential construction loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,109
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Three Years Prior to Current Year	2,580
Four Years Prior to Current Year	547
Five Years Prior to Current Year and Earlier	982
Total Loans	$ 4,109