Loans and allowance for loan losses - Loans evaluated for impairment (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	$ 3,370		$ 3,423
Allowance Individually Evaluated for Impairment	10					$ 11
Allowance Collectively Evaluated for Impairment	3,360					3,412
Loans Ending Balance	540,683		526,457			526,457
Loans Individually Evaluated for Impairment	7,567					9,243
Loans Collectively Evaluated for Impairment	533,116					517,214
Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	244	$ 228	286	$ 307	$ 269	499
Allowance Collectively Evaluated for Impairment	244					286
Loans Ending Balance	40,546		49,149			49,149
Loans Collectively Evaluated for Impairment	40,546					49,149
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	2,216	2,187	1,953	1,987	1,898	2,517
Allowance Individually Evaluated for Impairment	3					4
Allowance Collectively Evaluated for Impairment	2,213					1,949
Loans Ending Balance	289,921		255,537			255,537
Loans Individually Evaluated for Impairment	4,978					6,501
Loans Collectively Evaluated for Impairment	284,943					249,036
Consumer real estate secured by 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	179	175	182	212	196
Allowance Individually Evaluated for Impairment	6					7
Allowance Collectively Evaluated for Impairment	173					175
Loans Ending Balance	92,525		92,372			92,372
Loans Individually Evaluated for Impairment	2,476					2,557
Loans Collectively Evaluated for Impairment	90,049					89,815
Commercial and industrial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	3,370	3,423	3,423	3,443	3,429	3,970
Residential | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	69	57	57	76	66	214
Allowance Collectively Evaluated for Impairment	69					57
Loans Ending Balance	8,437		6,805			6,805
Loans Collectively Evaluated for Impairment	8,437					6,805
Commercial | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	175	171	229	231	203	285
Allowance Collectively Evaluated for Impairment	175					229
Loans Ending Balance	32,109		42,344			42,344
Loans Collectively Evaluated for Impairment	32,109					42,344
Owner occupied | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	875	868	833	860	802	1,047
Allowance Individually Evaluated for Impairment	3					4
Allowance Collectively Evaluated for Impairment	872					829
Loans Ending Balance	122,067		113,108			113,108
Loans Individually Evaluated for Impairment	4,389					5,043
Loans Collectively Evaluated for Impairment	117,678					108,065
Non-owner occupied | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	1,307	1,267	1,083	1,089	1,059	1,421
Allowance Collectively Evaluated for Impairment	1,307					1,083
Loans Ending Balance	155,981		129,786			129,786
Loans Individually Evaluated for Impairment	589					1,458
Loans Collectively Evaluated for Impairment	155,392					128,328
Multifamily | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	33	50	35	36	35	47
Allowance Collectively Evaluated for Impairment	33					35
Loans Ending Balance	11,309		11,666			11,666
Loans Collectively Evaluated for Impairment	11,309					11,666
Farmland | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	1	2	2	2	2	2
Allowance Collectively Evaluated for Impairment	1					2
Loans Ending Balance	564		977			977
Loans Collectively Evaluated for Impairment	564					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	11
Allowance Collectively Evaluated for Impairment	12					12
Loans Ending Balance	19,891		17,977			17,977
Loans Individually Evaluated for Impairment	300					300
Loans Collectively Evaluated for Impairment	19,591					17,677
First deed of trust | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	129	114
First deed of trust | Consumer real estate secured by 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	129		123	111	113	166
Allowance Individually Evaluated for Impairment	6					7
Allowance Collectively Evaluated for Impairment	123					116
Loans Ending Balance	65,704		62,277			62,277
Loans Individually Evaluated for Impairment	1,912					2,019
Loans Collectively Evaluated for Impairment	63,792					60,258
Second deed of trust | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	38	49
Second deed of trust | Consumer real estate secured by 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	38		47	90	72	79
Allowance Collectively Evaluated for Impairment	38					47
Loans Ending Balance	6,930		12,118			12,118
Loans Individually Evaluated for Impairment	264					238
Loans Collectively Evaluated for Impairment	6,666					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	582	533	486	480	422	408
Allowance Collectively Evaluated for Impairment	582					486
Loans Ending Balance	91,603		100,421			100,421
Loans Individually Evaluated for Impairment	89					185
Loans Collectively Evaluated for Impairment	91,514					100,236
Guaranteed student loans | Commercial and industrial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	67	60	65	70	80	87
Allowance Collectively Evaluated for Impairment	67					65
Loans Ending Balance	22,010		25,975			25,975
Loans Collectively Evaluated for Impairment	22,010					25,975
Consumer and other
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	82		451
Allowance Individually Evaluated for Impairment	1
Allowance Collectively Evaluated for Impairment	81					451
Loans Ending Balance	4,078					3,003
Loans Individually Evaluated for Impairment	24
Loans Collectively Evaluated for Impairment	4,054					3,003
Consumer and other | Commercial and industrial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	37	$ 45	29	$ 32	$ 36	$ 36
Loans Ending Balance	$ 4,078		$ 3,003