Loans and allowance For loan losses - Loans evaluated for credit losses (Details) - USD ($)	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for credit losses	$ 3,681,000	$ 3,574,000	$ 3,423,000	$ 3,256,000	$ 3,272,000	$ 3,370,000
Allowance Ending Balance	3,681,000	3,574,000	3,423,000	3,256,000	3,272,000	3,370,000
Allowance Individually Evaluated for Impairment	17,000		0
Allowance Collectively Evaluated for Impairment	3,664,000		3,423,000
Total loans	605,408,000		575,008,000
Loans Individually Evaluated for Impairment	387,000		291,000
Loans Collectively Evaluated for Impairment	605,021,000		574,717,000
Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for credit losses	290,000	259,000	314,000	328,000	315,000	271,000
Allowance Ending Balance	290,000	259,000	314,000	328,000	315,000	271,000
Allowance Collectively Evaluated for Impairment	290,000		314,000
Total loans	49,147,000		47,495,000
Loans Collectively Evaluated for Impairment	49,147,000		47,495,000
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for credit losses	2,015,000	2,119,000	1,923,000	1,795,000	1,891,000	2,189,000
Allowance Ending Balance	2,015,000	2,119,000	1,923,000	1,795,000	1,891,000	2,189,000
Allowance Collectively Evaluated for Impairment	2,015,000		1,923,000
Total loans	310,012,000		290,590,000
Loans Collectively Evaluated for Impairment	310,012,000		290,590,000
Consumer real estate secured by 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for credit losses	427,000	428,000	432,000	365,000	322,000	185,000
Allowance Ending Balance	427,000	428,000	432,000	365,000	322,000	185,000
Allowance Collectively Evaluated for Impairment	427,000		432,000
Total loans	130,285,000		128,532,000
Loans Individually Evaluated for Impairment	253,000		265,000
Loans Collectively Evaluated for Impairment	130,032,000		128,267,000
Residential | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for credit losses	84,000	57,000	86,000	61,000	51,000	79,000
Allowance Ending Balance	84,000	57,000	86,000	61,000	51,000	79,000
Allowance Collectively Evaluated for Impairment	84,000		86,000
Total loans	13,080,000		10,471,000
Loans Collectively Evaluated for Impairment	13,080,000		10,471,000
Commercial | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for credit losses	206,000	202,000	228,000	267,000	264,000	192,000
Allowance Ending Balance	206,000	202,000	228,000	267,000	264,000	192,000
Allowance Collectively Evaluated for Impairment	206,000		228,000
Total loans	36,067,000		37,024,000
Loans Collectively Evaluated for Impairment	36,067,000		37,024,000
Owner occupied | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for credit losses	461,000	437,000	409,000	379,000	391,000	867,000
Allowance Ending Balance	461,000	437,000	409,000	379,000	391,000	867,000
Allowance Collectively Evaluated for Impairment	461,000		409,000
Total loans	128,783,000		122,666,000
Loans Collectively Evaluated for Impairment	128,783,000		122,666,000
Non-owner occupied | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for credit losses	1,469,000	1,596,000	1,467,000	1,376,000	1,460,000	1,289,000
Allowance Ending Balance	1,469,000	1,596,000	1,467,000	1,376,000	1,460,000	1,289,000
Allowance Collectively Evaluated for Impairment	1,469,000		1,467,000
Total loans	162,621,000		154,855,000
Loans Collectively Evaluated for Impairment	162,621,000		154,855,000
Multifamily | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for credit losses	84,000	86,000	44,000	40,000	40,000	33,000
Allowance Ending Balance	84,000	86,000	44,000	40,000	40,000	33,000
Allowance Collectively Evaluated for Impairment	84,000		44,000
Total loans	18,293,000		12,743,000
Loans Collectively Evaluated for Impairment	18,293,000		12,743,000
Farmland | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for credit losses	1,000		3,000
Allowance Ending Balance	1,000		3,000
Allowance Collectively Evaluated for Impairment	1,000		3,000
Total loans	315,000		326,000
Loans Collectively Evaluated for Impairment	315,000		326,000
Home equity lines | Consumer real estate secured by 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for credit losses	32,000	32,000	40,000	63,000	33,000	11,000
Allowance Ending Balance	32,000	32,000	40,000	63,000	33,000	11,000
Allowance Collectively Evaluated for Impairment	32,000		40,000
Total loans	22,281,000		21,557,000
Loans Collectively Evaluated for Impairment	22,281,000		21,557,000
First deed of trust | Consumer real estate secured by 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for credit losses	292,000	298,000	293,000	219,000	214,000	131,000
Allowance Ending Balance	292,000	298,000	293,000	219,000	214,000	131,000
Allowance Collectively Evaluated for Impairment	292,000		293,000
Total loans	95,196,000		95,638,000
Loans Individually Evaluated for Impairment	157,000		160,000
Loans Collectively Evaluated for Impairment	95,039,000		95,478,000
Second deed of trust | Consumer real estate secured by 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for credit losses	103,000	98,000	99,000	83,000	75,000	43,000
Allowance Ending Balance	103,000	98,000	99,000	83,000	75,000	43,000
Allowance Collectively Evaluated for Impairment	103,000		99,000
Total loans	12,808,000		11,337,000
Loans Individually Evaluated for Impairment	96,000		105,000
Loans Collectively Evaluated for Impairment	12,712,000		11,232,000
Commercial and industrial loans (except those secured by real estate) | Commercial and industrial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for credit losses	726,000	666,000	640,000	673,000	549,000	576,000
Allowance Ending Balance	726,000	666,000	640,000	673,000	549,000	576,000
Allowance Individually Evaluated for Impairment	17,000
Allowance Collectively Evaluated for Impairment	709,000		640,000
Total loans	97,363,000		86,203,000
Loans Individually Evaluated for Impairment	134,000		26,000
Loans Collectively Evaluated for Impairment	97,229,000		86,177,000
Consumer Other and Unallocated [Member] | Consumer real estate secured by 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for credit losses			57,000
Allowance Ending Balance			57,000
Allowance Collectively Evaluated for Impairment			57,000
Total loans			4,265,000
Loans Collectively Evaluated for Impairment			4,265,000
Consumer Other and Unallocated [Member] | Commercial and industrial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for credit losses	178,000
Allowance Ending Balance	178,000
Allowance Collectively Evaluated for Impairment	178,000
Total loans	4,445,000
Loans Collectively Evaluated for Impairment	4,445,000
Guaranteed student loans | Commercial and industrial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for credit losses	45,000	55,000	57,000	13,000	112,000	52,000
Allowance Ending Balance	45,000	55,000	57,000	13,000	112,000	52,000
Allowance Collectively Evaluated for Impairment	45,000		57,000
Total loans	14,156,000		17,923,000
Loans Collectively Evaluated for Impairment	14,156,000		17,923,000
Consumer and other | Commercial and industrial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for credit losses	34,000	36,000	36,000	35,000	34,000	37,000
Allowance Ending Balance	34,000	$ 36,000	36,000	$ 35,000	$ 34,000	$ 37,000
Total loans	$ 4,445,000		$ 4,265,000