Loans and allowance for loan losses - Loans evaluated for impairment (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	$ 3,423		$ 3,423
Allowance Individually Evaluated for Impairment	28					$ 11
Allowance Collectively Evaluated for Impairment	3,395					3,412
Loans Ending Balance	527,556		526,457			526,457
Loans Individually Evaluated for Impairment	8,046					9,243
Loans Collectively Evaluated for Impairment	519,510					517,214
Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	228	$ 245	286	$ 269	$ 268	499
Allowance Collectively Evaluated for Impairment	228					286
Loans Ending Balance	37,028		49,149			49,149
Loans Collectively Evaluated for Impairment	37,028					49,149
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	2,187	2,037	1,953	1,898	2,224	2,517
Allowance Individually Evaluated for Impairment	3					4
Allowance Collectively Evaluated for Impairment	2,184					1,949
Loans Ending Balance	294,269		255,537			255,537
Loans Individually Evaluated for Impairment	5,514					6,501
Loans Collectively Evaluated for Impairment	288,755					249,036
Consumer real estate secured by 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	175	210	182	196	228
Allowance Individually Evaluated for Impairment	25					7
Allowance Collectively Evaluated for Impairment	150					175
Loans Ending Balance	83,969		92,372			92,372
Loans Individually Evaluated for Impairment	2,443					2,557
Loans Collectively Evaluated for Impairment	81,526					89,815
Commercial and industrial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	3,423	3,403	3,423	3,429	3,992	3,970
Residential | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	57	46	57	66	100	214
Allowance Collectively Evaluated for Impairment	57					57
Loans Ending Balance	7,026		6,805			6,805
Loans Collectively Evaluated for Impairment	7,026					6,805
Commercial | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	171	199	229	203	168	285
Allowance Collectively Evaluated for Impairment	171					229
Loans Ending Balance	30,002		42,344			42,344
Loans Collectively Evaluated for Impairment	30,002					42,344
Owner occupied | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	868	892	833	802	899	1,047
Allowance Individually Evaluated for Impairment	3					4
Allowance Collectively Evaluated for Impairment	865					829
Loans Ending Balance	124,496		113,108			113,108
Loans Individually Evaluated for Impairment	4,431					5,043
Loans Collectively Evaluated for Impairment	120,065					108,065
Non-owner occupied | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	1,267	1,106	1,083	1,059	1,286	1,421
Allowance Collectively Evaluated for Impairment	1,267					1,083
Loans Ending Balance	151,738		129,786			129,786
Loans Individually Evaluated for Impairment	1,083					1,458
Loans Collectively Evaluated for Impairment	150,655					128,328
Multifamily | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	50	37	35	35	38	47
Allowance Collectively Evaluated for Impairment	50					35
Loans Ending Balance	17,119		11,666			11,666
Loans Collectively Evaluated for Impairment	17,119					11,666
Farmland | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	2	2	2	2	1	2
Allowance Collectively Evaluated for Impairment	2					2
Loans Ending Balance	916		977			977
Loans Collectively Evaluated for Impairment	916					977
Home equity lines | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	12	12	12	11		24
Home equity lines | Consumer real estate secured by 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	12		12	11	15
Allowance Collectively Evaluated for Impairment	12					12
Loans Ending Balance	19,938		17,977			17,977
Loans Individually Evaluated for Impairment	300					300
Loans Collectively Evaluated for Impairment	19,638					17,677
First deed of trust | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	114	118
First deed of trust | Consumer real estate secured by 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	114		123	113	146	166
Allowance Individually Evaluated for Impairment	6					7
Allowance Collectively Evaluated for Impairment	108					116
Loans Ending Balance	58,378		62,277			62,277
Loans Individually Evaluated for Impairment	1,933					2,019
Loans Collectively Evaluated for Impairment	56,445					60,258
Second deed of trust | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	49	80
Second deed of trust | Consumer real estate secured by 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	49		47	72	67	79
Allowance Individually Evaluated for Impairment	19
Allowance Collectively Evaluated for Impairment	30					47
Loans Ending Balance	5,653		12,118			12,118
Loans Individually Evaluated for Impairment	210					238
Loans Collectively Evaluated for Impairment	5,443					11,880
Commercial and industrial loans (except those secured by real estate) | Commercial and industrial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	533	446	486	422	410	408
Allowance Collectively Evaluated for Impairment	533					486
Loans Ending Balance	85,119		100,421			100,421
Loans Individually Evaluated for Impairment	89					185
Loans Collectively Evaluated for Impairment	85,030					100,236
Guaranteed student loans | Commercial and industrial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	60	63	65	80	76	87
Allowance Collectively Evaluated for Impairment	60					65
Loans Ending Balance	23,413		25,975			25,975
Loans Collectively Evaluated for Impairment	23,413					25,975
Consumer and other
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	240		451
Allowance Collectively Evaluated for Impairment	240					451
Loans Ending Balance	3,758					3,003
Loans Collectively Evaluated for Impairment	3,758					3,003
Consumer and other | Commercial and industrial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	45	$ 35	29	$ 36	$ 38	$ 36
Loans Ending Balance	$ 3,758		$ 3,003