Loans and allowance for loan losses - Risk category of loans (Details) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current year	$ 73,289
One year prior	87,266		$ 88,151
Two years prior	94,294		100,297
Three years prior	88,433		96,010
Four years prior	44,266		48,576
Five years prior			29,814
Five years or more prior	152,663		146,610
Revolving	74,561		65,550
Total loans	614,772		575,008
Current-period gross write-offs
Current year	16
Total Current period gross writeoff	16	$ 23	33
Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	52,908		47,495
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	313,906		290,590
Consumer real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	130,664		128,532
Residential | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current year	8,364
One year prior	2,793		6,320
Two years prior	1,358		3,812
Three years prior	339		339
Revolving	3,807
Total loans	16,661		10,471
Residential | Construction and land development | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current year	8,364
One year prior	2,793		6,320
Two years prior	1,358		3,812
Three years prior	339		339
Revolving	3,807
Total loans	16,661		10,471
Commercial | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current year	4,349
One year prior	7,309		5,007
Two years prior	10,343		14,506
Three years prior	13,195		10,339
Four years prior	201		235
Five years or more prior	850		1,183
Revolving			5,754
Total loans	36,247		37,024
Commercial | Construction and land development | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current year	4,349
One year prior	7,309		5,007
Two years prior	10,343		14,506
Three years prior	13,195		10,339
Four years prior	201		235
Five years or more prior	850		1,183
Revolving			5,754
Total loans	36,247		37,024
Owner occupied | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current year	12,033
One year prior	13,238		11,945
Two years prior	23,203		22,048
Three years prior	18,798		20,117
Four years prior	9,497		9,855
Five years prior			12,145
Five years or more prior	51,328		45,768
Revolving	1,650		788
Total loans	129,747		122,666
Owner occupied | Commercial real estate | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current year	12,033
One year prior	13,238		11,945
Two years prior	23,203		21,846
Three years prior	18,798		20,044
Four years prior	9,497		9,855
Five years prior			12,145
Five years or more prior	48,221		41,067
Revolving	1,650		788
Total loans	126,640		117,690
Owner occupied | Commercial real estate | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Two years prior			202
Three years prior			73
Five years or more prior	3,107		4,701
Total loans	3,107		4,976
Non-owner occupied | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current year	11,725
One year prior	11,463		9,468
Two years prior	29,220		25,607
Three years prior	29,391		30,628
Four years prior	22,869		23,567
Five years prior			9,528
Five years or more prior	56,584		52,745
Revolving	4,727		3,312
Total loans	165,979		154,855
Non-owner occupied | Commercial real estate | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current year	11,725
One year prior	11,463		9,468
Two years prior	29,220		25,607
Three years prior	27,256		28,455
Four years prior	22,869		23,567
Five years prior			9,528
Five years or more prior	53,861		47,645
Revolving	4,727		3,312
Total loans	161,121		147,582
Non-owner occupied | Commercial real estate | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Three years prior	2,135		2,173
Five years or more prior	2,723		5,100
Total loans	4,858		7,273
Multifamily | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current year	5,249
One year prior	1,300		1,300
Three years prior	2,293		2,503
Four years prior	257		548
Five years prior			885
Five years or more prior	6,654		6,113
Revolving	2,109		1,394
Total loans	17,862		12,743
Multifamily | Commercial real estate | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current year	5,249
One year prior	1,300		1,300
Three years prior	2,293		2,503
Four years prior	257		548
Five years prior			885
Five years or more prior	6,654		6,113
Revolving	2,109		1,394
Total loans	17,862		12,743
Farmland | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Five years or more prior	18		26
Revolving	300		300
Total loans	318		326
Farmland | Commercial real estate | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Five years or more prior	18		26
Revolving	300		300
Total loans	318		326
Home equity lines | Consumer real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Two years prior			446
Revolving	22,384		21,111
Total loans	22,384		21,557
Home equity lines | Consumer real estate | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Two years prior			446
Revolving	22,239		21,036
Total loans	22,239		21,482
Home equity lines | Consumer real estate | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revolving			75
Total loans			75
Home equity lines | Consumer real estate | Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revolving	145
Total loans	145
First deed of trust | Consumer real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current year	12,170
One year prior	30,251		34,067
Two years prior	13,909		14,288
Three years prior	13,587		15,613
Four years prior	6,696		8,277
Five years prior			2,957
Five years or more prior	17,884		18,311
Revolving			2,125
Total loans	94,497		95,638
First deed of trust | Consumer real estate | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current year	12,170
One year prior	27,947		34,067
Two years prior	13,909		14,288
Three years prior	13,587		15,613
Four years prior	6,696		8,107
Five years prior			2,957
Five years or more prior	17,521		17,427
Revolving			2,125
Total loans	91,830		94,584
First deed of trust | Consumer real estate | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
One year prior	2,304
Four years prior			170
Five years or more prior	207		724
Total loans	2,511		894
First deed of trust | Consumer real estate | Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Five years or more prior	156		160
Total loans	156		160
Second deed of trust | Consumer real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current year	3,760
One year prior	4,140		4,530
Two years prior	2,906		3,207
Three years prior	879		1,027
Four years prior	362		397
Five years prior			1,112
Five years or more prior	1,447		798
Revolving	289		266
Total loans	13,783		11,337
Second deed of trust | Consumer real estate | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current year	3,673
One year prior	4,140		4,530
Two years prior	2,906		3,207
Three years prior	879		1,027
Four years prior	362		397
Five years prior			1,067
Five years or more prior	1,256		626
Revolving	289		266
Total loans	13,505		11,120
Second deed of trust | Consumer real estate | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current year	87
Five years prior			45
Five years or more prior	106		67
Total loans	193		112
Second deed of trust | Consumer real estate | Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Five years or more prior	85		105
Total loans	85		105
Commercial and industrial loans (except those secured by real estate) | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current year	15,243
One year prior	16,463		15,059
Two years prior	13,030		15,900
Three years prior	9,894		15,321
Four years prior	4,363		5,647
Five years prior			3,170
Five years or more prior	4,229		3,732
Revolving	35,656		27,374
Total loans	98,878		86,203
Commercial and industrial loans (except those secured by real estate) | Commercial and industrial loans | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current year	15,243
One year prior	16,463		15,022
Two years prior	12,945		15,900
Three years prior	9,815		15,321
Four years prior	4,363		5,634
Five years prior			2,852
Five years or more prior	4,113		3,698
Revolving	34,809		27,068
Total loans	97,751		85,495
Commercial and industrial loans (except those secured by real estate) | Commercial and industrial loans | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
One year prior			37
Two years prior	85
Five years prior			318
Five years or more prior	92		22
Revolving	847		306
Total loans	1,024		683
Commercial and industrial loans (except those secured by real estate) | Commercial and industrial loans | Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Three years prior	79
Four years prior			13
Five years or more prior	24		12
Total loans	103		25
Guaranteed student loans | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Five years or more prior	13,645		17,923
Total loans	13,645		17,923
Current-period gross write-offs
Current year	16
One year prior			30
Total Current period gross writeoff	16	21	30
Guaranteed student loans | Commercial and industrial loans | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Five years or more prior	13,645		17,923
Total loans	13,645		17,923
Consumer and other | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current year	396
One year prior	309		455
Two years prior	325		483
Three years prior	57		123
Four years prior	21		50
Five years prior			17
Five years or more prior	24		11
Revolving	3,639		3,126
Total loans	4,771		4,265
Current-period gross write-offs
One year prior			3
Total Current period gross writeoff		$ 2	3
Consumer and other | Commercial and industrial loans | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current year	396
One year prior	309		455
Two years prior	325		483
Three years prior	57		123
Four years prior	21		50
Five years prior			17
Five years or more prior	24		11
Revolving	3,639		3,126
Total loans	$ 4,771		$ 4,265