Loans and allowance for credit losses - Allowance for loan losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 3,370	$ 3,423
Provision for (Recovery of) Loan Losses		(300)
Charge-offs		(217)
Recoveries		464
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	3,370	3,423
Provision for (Recovery of) Credit Losses	21
Charge-offs	(33)
Recoveries	192
Ending Balance	3,423	3,370
Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Ending Balance	(127)
Consumer and other
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	97
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	97
Ending Balance	57	97
Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	271	286
Provision for (Recovery of) Loan Losses		(15)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	271	286
Provision for (Recovery of) Credit Losses	6
Ending Balance	314	271
Construction and land development | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Ending Balance	37
Construction and land development | Residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	79	57
Provision for (Recovery of) Loan Losses		22
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	79	57
Provision for (Recovery of) Credit Losses	4
Ending Balance	86	79
Construction and land development | Residential | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Ending Balance	3
Construction and land development | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	192	229
Provision for (Recovery of) Loan Losses		(37)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	192	229
Provision for (Recovery of) Credit Losses	2
Ending Balance	228	192
Construction and land development | Commercial | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Ending Balance	34
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	2,189	1,953
Provision for (Recovery of) Loan Losses		236
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	2,189	1,953
Provision for (Recovery of) Credit Losses	10
Ending Balance	1,923	2,189
Commercial real estate | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Ending Balance	(276)
Commercial real estate | Owner occupied
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	867	833
Provision for (Recovery of) Loan Losses		34
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	867	833
Provision for (Recovery of) Credit Losses	17
Ending Balance	409	867
Commercial real estate | Owner occupied | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Ending Balance	(475)
Commercial real estate | Non-owner occupied
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,289	1,083
Provision for (Recovery of) Loan Losses		206
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,289	1,083
Provision for (Recovery of) Credit Losses	(14)
Ending Balance	1,467	1,289
Commercial real estate | Non-owner occupied | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Ending Balance	192
Commercial real estate | Multifamily
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	33	35
Provision for (Recovery of) Loan Losses		(2)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	33	35
Provision for (Recovery of) Credit Losses	4
Ending Balance	44	33
Commercial real estate | Multifamily | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Ending Balance	7
Commercial real estate | Farmland
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	0	2
Provision for (Recovery of) Loan Losses		(2)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	0	2
Provision for (Recovery of) Credit Losses	3
Ending Balance	3	0
Consumer real estate secured by 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	185	182
Provision for (Recovery of) Loan Losses		(367)
Charge-offs		(27)
Recoveries		397
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	185	182
Provision for (Recovery of) Credit Losses	103
Recoveries	19
Ending Balance	432	185
Consumer real estate secured by 1-4 family residential | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Ending Balance	125
Consumer real estate secured by 1-4 family residential | Home equity lines
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	11	12
Provision for (Recovery of) Loan Losses		(59)
Recoveries		58
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	11	12
Provision for (Recovery of) Credit Losses	5
Ending Balance	40	11
Consumer real estate secured by 1-4 family residential | Home equity lines | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Ending Balance	24
Consumer real estate secured by 1-4 family residential | First deed of trust
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	131	123
Provision for (Recovery of) Loan Losses		3
Recoveries		5
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	131	123
Provision for (Recovery of) Credit Losses	83
Recoveries	3
Ending Balance	293	131
Consumer real estate secured by 1-4 family residential | First deed of trust | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Ending Balance	76
Consumer real estate secured by 1-4 family residential | Second deed of trust
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	43	47
Provision for (Recovery of) Loan Losses		(311)
Charge-offs		(27)
Recoveries		334
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	43	47
Provision for (Recovery of) Credit Losses	15
Recoveries	16
Ending Balance	99	43
Consumer real estate secured by 1-4 family residential | Second deed of trust | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Ending Balance	25
Commercial and industrial loans | Commercial and industrial loans (except those secured by real estate)
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	576	486
Provision for (Recovery of) Loan Losses		180
Charge-offs		(157)
Recoveries		67
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	576	486
Provision for (Recovery of) Credit Losses	(110)
Recoveries	173
Ending Balance	640	576
Commercial and industrial loans | Commercial and industrial loans (except those secured by real estate) | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Ending Balance	1
Commercial and industrial loans | Student loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	52	65
Provision for (Recovery of) Loan Losses		18
Charge-offs		(31)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	52	65
Provision for (Recovery of) Credit Losses	35
Charge-offs	(30)
Ending Balance	57	52
Commercial and industrial loans | Consumer and other
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	37	29
Provision for (Recovery of) Loan Losses		10
Charge-offs		(2)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	37	29
Provision for (Recovery of) Credit Losses	7
Charge-offs	(3)
Ending Balance	36	37
Commercial and industrial loans | Consumer and other | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Ending Balance	(5)
Commercial and industrial loans | Unallocated
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	60	422
Provision for (Recovery of) Loan Losses		(362)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	60	422
Provision for (Recovery of) Credit Losses	(30)
Ending Balance	21	$ 60
Commercial and industrial loans | Unallocated | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Ending Balance	$ (9)