Loans and allowance for credit losses - Allowance for credit losses on loans losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 3,574	$ 3,272	$ 3,423	$ 3,370	$ 3,370
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	3,574	3,272	3,423	3,370	3,370
Provision for (Recovery of) Credit Losses		(22)	137	1	(21)
Charge-offs			(11)	(7)	(33)
Charge-offs	(5)	(4)			(33)
Recoveries	112	10	132	19	192
Ending Balance	3,681	3,256	3,681	3,256	3,423
Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Impact of adoption ASC 326				(127)	(127)
Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	259	315	314	271	271
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	259	315	314	271	271
Provision for (Recovery of) Credit Losses	31	13	(24)	20	(6)
Ending Balance	290	328	290	328	314
Construction and land development | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Impact of adoption ASC 326				37	37
Construction and land development | Residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	57	51	86	79	79
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	57	51	86	79	79
Provision for (Recovery of) Credit Losses	27	10	(2)	(21)	(4)
Ending Balance	84	61	84	61	86
Construction and land development | Residential | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Impact of adoption ASC 326				3	3
Construction and land development | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	202	264	228	192	192
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	202	264	228	192	192
Provision for (Recovery of) Credit Losses	4	3	(22)	41	(2)
Ending Balance	206	267	206	267	228
Construction and land development | Commercial | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Impact of adoption ASC 326				34	34
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	2,119	1,891	1,923	2,189	2,189
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	2,119	1,891	1,923	2,189	2,189
Provision for (Recovery of) Credit Losses	(104)	(96)	92	(118)	(10)
Ending Balance	2,015	1,795	2,015	1,795	1,923
Commercial real estate | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Impact of adoption ASC 326				(276)	(276)
Commercial real estate | Owner occupied
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	437	391	409	867	867
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	437	391	409	867	867
Provision for (Recovery of) Credit Losses	24	(12)	52	(13)	(17)
Ending Balance	461	379	461	379	409
Commercial real estate | Owner occupied | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Impact of adoption ASC 326				(475)	(475)
Commercial real estate | Non-owner occupied
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,596	1,460	1,467	1,289	1,289
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,596	1,460	1,467	1,289	1,289
Provision for (Recovery of) Credit Losses	(127)	(84)	2	(105)	14
Ending Balance	1,469	1,376	1,469	1,376	1,467
Commercial real estate | Non-owner occupied | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Impact of adoption ASC 326				192	192
Commercial real estate | Multifamily
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	86	40	44	33	33
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	86	40	44	33	33
Provision for (Recovery of) Credit Losses	(2)		40		(4)
Ending Balance	84	40	84	40	44
Commercial real estate | Multifamily | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Impact of adoption ASC 326				7	7
Commercial real estate | Farmland
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance			3
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance			3
Provision for (Recovery of) Credit Losses	1		(2)		(3)
Ending Balance	1		1		3
Consumer real estate secured by 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	428	322	432	185	185
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	428	322	432	185	185
Provision for (Recovery of) Credit Losses	(110)	39	(130)	48	(103)
Recoveries	109	4	125	7	19
Ending Balance	427	365	427	365	432
Consumer real estate secured by 1-4 family residential | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Impact of adoption ASC 326				125	125
Consumer real estate secured by 1-4 family residential | Home equity lines
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	32	33	40	11	11
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	32	33	40	11	11
Provision for (Recovery of) Credit Losses		30	(18)	28	(5)
Recoveries			10
Ending Balance	32	63	32	63	40
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]
Impact of adoption ASC 326				24	24
Consumer real estate secured by 1-4 family residential | First deed of trust
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	298	214	293	131	131
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	298	214	293	131	131
Provision for (Recovery of) Credit Losses	(7)	5	(3)	11	(83)
Recoveries	1		2	1	3
Ending Balance	292	219	292	219	293
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]
Impact of adoption ASC 326				76	76
Consumer real estate secured by 1-4 family residential | Second deed of trust
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	98	75	99	43	43
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	98	75	99	43	43
Provision for (Recovery of) Credit Losses	(103)	4	(109)	9	(15)
Recoveries	108	4	113	6	16
Ending Balance	103	83	103	83	99
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]
Impact of adoption ASC 326				25	25
Consumer real estate secured by 1-4 family residential | Consumer Other and Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance			57
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance			57
Ending Balance					57
Commercial and industrial loans | Commercial and industrial loans (except those secured by real estate)
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	666	549	640	576	576
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	666	549	640	576	576
Provision for (Recovery of) Credit Losses	57	118	79	84	110
Recoveries	3	6	7	12	173
Ending Balance	726	673	726	673	640
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]
Impact of adoption ASC 326				1	1
Commercial and industrial loans | Student loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	55	112	57	52	52
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	55	112	57	52	52
Provision for (Recovery of) Credit Losses	(5)	(95)	(1)	(32)	(35)
Charge-offs			(11)	(7)	(30)
Charge-offs	(5)	(4)			(30)
Ending Balance	45	13	45	13	57
Commercial and industrial loans | Consumer Other and Unallocated [Member]
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Ending Balance	178		178
Commercial and industrial loans | Consumer and other
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	36	34	36	37	37
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	36	34	36	37	37
Provision for (Recovery of) Credit Losses	(2)	1	(2)	3	(7)
Charge-offs					(3)
Charge-offs					(3)
Ending Balance	34	35	34	35	36
Commercial and industrial loans | Consumer and other | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Impact of adoption ASC 326				(5)	(5)
Commercial and industrial loans | Unallocated
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	11	49	21	60	60
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	11	49	21	60	60
Provision for (Recovery of) Credit Losses	133	(2)	123	(4)	30
Ending Balance	$ 144	$ 47	$ 144	47	21
Commercial and industrial loans | Unallocated | Adoption of ASC 326
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Impact of adoption ASC 326				$ (9)	$ (9)