Loans and allowances for loan losses - Classified by type (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less: allowance for credit losses	$ (3,700)	$ (3,681)	$ (3,423)	$ (3,353)	$ (3,256)	$ (3,370)
Percentage of class of loans to loan portfolio (in percent)	100.00%		100.00%
Loans
Total loans	$ 614,772		$ 575,008
Deferred (fees) and costs, net	612		803
Less: allowance for credit losses	(3,700)	(3,681)	(3,423)	(3,353)	(3,256)	(3,370)
Total loans, net	611,684		572,388
Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less: allowance for credit losses	$ (314)	(290)	$ (314)	(365)	(329)	(271)
Percentage of class of loans to loan portfolio (in percent)	8.61%		8.26%
Loans
Total loans	$ 52,908		$ 47,495
Less: allowance for credit losses	(314)	(290)	(314)	(365)	(329)	(271)
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less: allowance for credit losses	$ (2,024)	(2,015)	$ (1,923)	(1,879)	(1,799)	(2,189)
Percentage of class of loans to loan portfolio (in percent)	51.06%		50.54%
Loans
Total loans	$ 313,906		$ 290,590
Less: allowance for credit losses	(2,024)	(2,015)	(1,923)	(1,879)	(1,799)	(2,189)
Consumer real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less: allowance for credit losses	$ (425)	(427)	$ (432)	(396)	(361)	(185)
Percentage of class of loans to loan portfolio (in percent)	21.25%		22.35%
Loans
Total loans	$ 130,664		$ 128,532
Less: allowance for credit losses	(425)	(427)	(432)	(396)	(361)	(185)
Residential | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less: allowance for credit losses	$ (102)	(84)	$ (86)	(73)	(61)	(79)
Percentage of class of loans to loan portfolio (in percent)	2.71%		1.82%
Loans
Total loans	$ 16,661		$ 10,471
Less: allowance for credit losses	(102)	(84)	(86)	(73)	(61)	(79)
Commercial | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less: allowance for credit losses	$ (212)	(206)	$ (228)	(292)	(268)	(192)
Percentage of class of loans to loan portfolio (in percent)	5.90%		6.44%
Loans
Total loans	$ 36,247		$ 37,024
Less: allowance for credit losses	(212)	(206)	(228)	(292)	(268)	(192)
Owner occupied | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less: allowance for credit losses	$ (466)	(461)	$ (409)	(397)	(379)	(867)
Percentage of class of loans to loan portfolio (in percent)	21.10%		21.33%
Loans
Total loans	$ 129,747		$ 122,666
Less: allowance for credit losses	(466)	(461)	(409)	(397)	(379)	(867)
Non-owner occupied | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less: allowance for credit losses	$ (1,483)	(1,469)	$ (1,467)	(1,435)	(1,376)	(1,289)
Percentage of class of loans to loan portfolio (in percent)	27.00%		26.93%
Loans
Total loans	$ 165,979		$ 154,855
Less: allowance for credit losses	(1,483)	(1,469)	(1,467)	(1,435)	(1,376)	(1,289)
Multifamily | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less: allowance for credit losses	$ (74)	(84)	$ (44)	(44)	(44)	(33)
Percentage of class of loans to loan portfolio (in percent)	2.91%		2.22%
Loans
Total loans	$ 17,862		$ 12,743
Less: allowance for credit losses	(74)	(84)	(44)	(44)	(44)	(33)
Farmland | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less: allowance for credit losses	$ (1)	(1)	$ (3)	(3)
Percentage of class of loans to loan portfolio (in percent)	0.05%		0.06%
Loans
Total loans	$ 318		$ 326
Less: allowance for credit losses	(1)	(1)	(3)	(3)
Home equity lines | Consumer real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less: allowance for credit losses	$ (33)	(32)	$ (40)	(34)	(32)	(11)
Percentage of class of loans to loan portfolio (in percent)	3.64%		3.75%
Loans
Total loans	$ 22,384		$ 21,557
Less: allowance for credit losses	(33)	(32)	(40)	(34)	(32)	(11)
First deed of trust | Consumer real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less: allowance for credit losses	$ (279)	(292)	$ (293)	(270)	(245)	(131)
Percentage of class of loans to loan portfolio (in percent)	15.37%		16.63%
Loans
Total loans	$ 94,497		$ 95,638
Less: allowance for credit losses	(279)	(292)	(293)	(270)	(245)	(131)
Second deed of trust | Consumer real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less: allowance for credit losses	$ (113)	(103)	$ (99)	(92)	(84)	(43)
Percentage of class of loans to loan portfolio (in percent)	2.24%		1.97%
Loans
Total loans	$ 13,783		$ 11,337
Less: allowance for credit losses	(113)	(103)	(99)	(92)	(84)	(43)
Commercial and industrial loans (except those secured by real estate) | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less: allowance for credit losses	$ (732)	(726)	$ (640)	(610)	(673)	(576)
Percentage of class of loans to loan portfolio (in percent)	16.08%		14.99%
Loans
Total loans	$ 98,878		$ 86,203
Less: allowance for credit losses	(732)	(726)	(640)	(610)	(673)	(576)
Guaranteed student loans | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less: allowance for credit losses	$ (41)	(45)	$ (57)	(46)	(44)	(52)
Percentage of class of loans to loan portfolio (in percent)	2.22%		3.12%
Loans
Total loans	$ 13,645		$ 17,923
Less: allowance for credit losses	(41)	(45)	(57)	(46)	(44)	(52)
Consumer and other | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less: allowance for credit losses	$ (34)	(34)	$ (36)	(35)	(34)	(37)
Percentage of class of loans to loan portfolio (in percent)	0.78%		0.74%
Loans
Total loans	$ 4,771		$ 4,265
Less: allowance for credit losses	$ (34)	$ (34)	$ (36)	$ (35)	$ (34)	$ (37)