Loans and allowance for loan losses - Allowance for loan losses (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance			$ 3,423,000
Provision for (Recovery of) Loan Losses		$ (500,000)	(400,000)	$ (500,000)
Ending Balance	$ 3,423,000		3,423,000		$ 3,423,000
Consumer Real Estate Secured By 1-4 Family Residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance				269,000	269,000
Provision for (Recovery of) Loan Losses				(25,000)
Charge-offs				(84,000)
Recoveries				36,000
Ending Balance		196,000		196,000
Consumer and other
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance			451,000
Ending Balance	240,000		240,000		451,000
Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	245,000	268,000	286,000	499,000	499,000
Provision for (Recovery of) Loan Losses	(17,000)	1,000	(58,000)	(230,000)	(213,000)
Ending Balance	228,000	269,000	228,000	269,000	286,000
Construction and land development | Residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	46,000	100,000	57,000	214,000	214,000
Provision for (Recovery of) Loan Losses	11,000	(34,000)		(148,000)	(157,000)
Ending Balance	57,000	66,000	57,000	66,000	57,000
Construction and land development | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	199,000	168,000	229,000	285,000	285,000
Provision for (Recovery of) Loan Losses	(28,000)	35,000	(58,000)	(82,000)	(56,000)
Ending Balance	171,000	203,000	171,000	203,000	229,000
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	2,037,000	2,224,000	1,953,000	2,517,000	2,517,000
Provision for (Recovery of) Loan Losses	150,000	(340,000)	234,000	(633,000)	(578,000)
Recoveries		14,000		14,000	14,000
Ending Balance	2,187,000	1,898,000	2,187,000	1,898,000	1,953,000
Commercial real estate | Owner occupied
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	892,000	899,000	833,000	1,047,000	1,047,000
Provision for (Recovery of) Loan Losses	(24,000)	(97,000)	35,000	(245,000)	(214,000)
Ending Balance	868,000	802,000	868,000	802,000	833,000
Commercial real estate | Non-owner occupied
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	1,106,000	1,286,000	1,083,000	1,421,000	1,421,000
Provision for (Recovery of) Loan Losses	161,000	(241,000)	184,000	(376,000)	(352,000)
Recoveries		14,000		14,000	14,000
Ending Balance	1,267,000	1,059,000	1,267,000	1,059,000	1,083,000
Commercial real estate | Multifamily
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	37,000	38,000	35,000	47,000	47,000
Provision for (Recovery of) Loan Losses	13,000	(3,000)	15,000	(12,000)	(12,000)
Ending Balance	50,000	35,000	50,000	35,000	35,000
Commercial real estate | Farmland
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	2,000	1,000	2,000	2,000	2,000
Provision for (Recovery of) Loan Losses		1,000
Ending Balance	2,000	2,000	2,000	2,000	2,000
Commercial real estate | Home equity lines
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	12,000		12,000	24,000	24,000
Provision for (Recovery of) Loan Losses			(58,000)	(23,000)	(23,000)
Recoveries			58,000	10,000	11,000
Ending Balance	12,000	11,000	12,000	11,000	12,000
Commercial real estate | Consumer Real Estate Secured By 1-4 Family Residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance			182,000	269,000	269,000
Provision for (Recovery of) Loan Losses					(76,000)
Charge-offs					(84,000)
Recoveries					73,000
Ending Balance					182,000
Commercial real estate | First deed of trust
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	118,000
Provision for (Recovery of) Loan Losses	(5,000)
Recoveries	1,000
Ending Balance	114,000		114,000
Commercial real estate | Second deed of trust
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	80,000
Provision for (Recovery of) Loan Losses	(32,000)
Recoveries	1,000
Ending Balance	49,000		49,000
Consumer real estate secured by 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	210,000	228,000	182,000
Provision for (Recovery of) Loan Losses	(37,000)	31,000	(370,000)
Charge-offs		(84,000)
Recoveries	2,000	21,000	363,000
Ending Balance	175,000	196,000	175,000	196,000	182,000
Consumer real estate secured by 1-4 family residential | Home equity lines
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance		15,000	12,000
Provision for (Recovery of) Loan Losses		(14,000)
Recoveries		10,000
Ending Balance	12,000	11,000	12,000	11,000	12,000
Consumer real estate secured by 1-4 family residential | First deed of trust
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance		146,000	123,000	166,000	166,000
Provision for (Recovery of) Loan Losses		(41,000)	(11,000)	(62,000)	(54,000)
Recoveries		8,000	2,000	9,000	11,000
Ending Balance	114,000	113,000	114,000	113,000	123,000
Consumer real estate secured by 1-4 family residential | Second deed of trust
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance		67,000	47,000	79,000	79,000
Provision for (Recovery of) Loan Losses		86,000	(301,000)	60,000	1,000
Charge-offs		(84,000)		(84,000)	(84,000)
Recoveries		3,000	303,000	17,000	51,000
Ending Balance	49,000	72,000	49,000	72,000	47,000
Commercial and industrial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	3,403,000	3,992,000	3,423,000	3,970,000	3,970,000
Provision for (Recovery of) Loan Losses		(500,000)	(400,000)	(500,000)	(500,000)
Charge-offs	(13,000)	(107,000)	(22,000)	(115,000)	(165,000)
Recoveries	33,000	44,000	422,000	74,000	118,000
Ending Balance	3,423,000	3,429,000	3,423,000	3,429,000	3,423,000
Commercial and industrial loans | Commercial and industrial loans (except those secured by real estate)
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	446,000	410,000	486,000	408,000	408,000
Provision for (Recovery of) Loan Losses	56,000	3,000	(12,000)	(10,000)	47,000
Recoveries	31,000	9,000	59,000	24,000	31,000
Ending Balance	533,000	422,000	533,000	422,000	486,000
Commercial and industrial loans | Guaranteed student loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	63,000	76,000	65,000	87,000	87,000
Provision for (Recovery of) Loan Losses	10,000	9,000	17,000	6,000	13,000
Charge-offs	(13,000)	(5,000)	(22,000)	(13,000)	(35,000)
Ending Balance	60,000	80,000	60,000	80,000	65,000
Commercial and industrial loans | Consumer and other
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	35,000	38,000	29,000	36,000	36,000
Provision for (Recovery of) Loan Losses	10,000	16,000	16,000	18,000	39,000
Charge-offs		(18,000)		(18,000)	(46,000)
Ending Balance	45,000	36,000	45,000	36,000	29,000
Commercial and industrial loans | Unallocated
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	367,000	748,000	422,000	154,000	154,000
Provision for (Recovery of) Loan Losses	(172,000)	(220,000)	(227,000)	374,000	268,000
Ending Balance	$ 195,000	$ 528,000	$ 195,000	$ 528,000	$ 422,000