Loans and allowance for credit losses - Loans evaluated for impairment (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance			$ 3,370	$ 3,423	$ 3,403	$ 3,423
Allowance Ending Balance	$ 3,256	$ 3,272
Allowance Individually Evaluated for Impairment			9
Allowance Collectively Evaluated for Impairment			3,361
Allowance Collectively Evaluated For Impairment, after ASU 2016-13	3,256
Loans Ending Balance			538,427
Total loans	556,170
Loans Individually Evaluated for Impairment			7,311
Loans Individually Evaluated For Impairment, after ASU 2016-13	2,071
Loans Collectively Evaluated for Impairment			531,116
Loans Collectively Evaluated For Impairment, after ASU 2016-13	554,099
Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance			271	228	245	286
Allowance Ending Balance	328	315
Allowance Collectively Evaluated for Impairment			271
Allowance Collectively Evaluated For Impairment, after ASU 2016-13	328
Loans Ending Balance			45,127
Total loans	50,938
Loans Collectively Evaluated for Impairment			45,127
Loans Collectively Evaluated For Impairment, after ASU 2016-13	50,938
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance			2,189	2,187	2,037	1,953
Allowance Ending Balance	1,795	1,891
Allowance Individually Evaluated for Impairment			2
Allowance Collectively Evaluated for Impairment			2,187
Allowance Collectively Evaluated For Impairment, after ASU 2016-13	1,795
Loans Ending Balance			284,617
Total loans	282,921
Loans Individually Evaluated for Impairment			4,895
Loans Individually Evaluated For Impairment, after ASU 2016-13	1,714
Loans Collectively Evaluated for Impairment			279,722
Loans Collectively Evaluated For Impairment, after ASU 2016-13	281,207
Consumer real estate secured by 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance			185	175	210	182
Allowance Ending Balance	365	322
Allowance Individually Evaluated for Impairment			6
Allowance Collectively Evaluated for Impairment			179
Allowance Collectively Evaluated For Impairment, after ASU 2016-13	365
Loans Ending Balance			93,680
Total loans	106,532
Loans Individually Evaluated for Impairment			2,376
Loans Individually Evaluated For Impairment, after ASU 2016-13	271
Loans Collectively Evaluated for Impairment			91,304
Loans Collectively Evaluated For Impairment, after ASU 2016-13	106,261
Residential | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance			79	57	46	57
Allowance Ending Balance	61	51
Allowance Collectively Evaluated for Impairment			79
Allowance Collectively Evaluated For Impairment, after ASU 2016-13	61
Loans Ending Balance			9,727
Total loans	7,527
Loans Collectively Evaluated for Impairment			9,727
Loans Collectively Evaluated For Impairment, after ASU 2016-13	7,527
Commercial | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance			192	171	199	229
Allowance Ending Balance	267	264
Allowance Collectively Evaluated for Impairment			192
Allowance Collectively Evaluated For Impairment, after ASU 2016-13	267
Loans Ending Balance			35,400
Total loans	43,411
Loans Collectively Evaluated for Impairment			35,400
Loans Collectively Evaluated For Impairment, after ASU 2016-13	43,411
Owner occupied | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance			867	868	892	833
Allowance Ending Balance	379	391
Allowance Individually Evaluated for Impairment			2
Allowance Collectively Evaluated for Impairment			865
Allowance Collectively Evaluated For Impairment, after ASU 2016-13	379
Loans Ending Balance			119,643
Total loans	114,964
Loans Individually Evaluated for Impairment			4,583
Loans Individually Evaluated For Impairment, after ASU 2016-13	1,714
Loans Collectively Evaluated for Impairment			115,060
Loans Collectively Evaluated For Impairment, after ASU 2016-13	113,250
Non-owner occupied | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance			1,289	1,267	1,106	1,083
Allowance Ending Balance	1,376	1,460
Allowance Collectively Evaluated for Impairment			1,289
Allowance Collectively Evaluated For Impairment, after ASU 2016-13	1,376
Loans Ending Balance			153,610
Total loans	155,139
Loans Individually Evaluated for Impairment			312
Loans Collectively Evaluated for Impairment			153,298
Loans Collectively Evaluated For Impairment, after ASU 2016-13	155,139
Multifamily | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance			33	50	37	35
Allowance Ending Balance	40	40
Allowance Collectively Evaluated for Impairment			33
Allowance Collectively Evaluated For Impairment, after ASU 2016-13	40
Loans Ending Balance			11,291
Total loans	12,755
Loans Collectively Evaluated for Impairment			11,291
Loans Collectively Evaluated For Impairment, after ASU 2016-13	12,755
Farmland | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance				2	2	2
Loans Ending Balance			73
Total loans	63
Loans Collectively Evaluated for Impairment			73
Loans Collectively Evaluated For Impairment, after ASU 2016-13	63
Home equity lines | Consumer real estate secured by 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance			11	12	12	12
Allowance Ending Balance	63	33
Allowance Collectively Evaluated for Impairment			11
Allowance Collectively Evaluated For Impairment, after ASU 2016-13	63
Loans Ending Balance			18,421
Total loans	17,335
Loans Individually Evaluated for Impairment			300
Loans Collectively Evaluated for Impairment			18,121
Loans Collectively Evaluated For Impairment, after ASU 2016-13	17,335
First deed of trust | Consumer real estate secured by 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance			131	114	118	123
Allowance Ending Balance	219	214
Allowance Individually Evaluated for Impairment			6
Allowance Collectively Evaluated for Impairment			125
Allowance Collectively Evaluated For Impairment, after ASU 2016-13	219
Loans Ending Balance			67,495
Total loans	79,762
Loans Individually Evaluated for Impairment			1,881
Loans Individually Evaluated For Impairment, after ASU 2016-13	162
Loans Collectively Evaluated for Impairment			65,614
Loans Collectively Evaluated For Impairment, after ASU 2016-13	79,600
Second deed of trust | Consumer real estate secured by 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance			43	49	80	47
Allowance Ending Balance	83	75
Allowance Collectively Evaluated for Impairment			43
Allowance Collectively Evaluated For Impairment, after ASU 2016-13	83
Loans Ending Balance			7,764
Total loans	9,435
Loans Individually Evaluated for Impairment			195
Loans Individually Evaluated For Impairment, after ASU 2016-13	109
Loans Collectively Evaluated for Impairment			7,569
Loans Collectively Evaluated For Impairment, after ASU 2016-13	9,326
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			576	533	446	486
Allowance Ending Balance	673	549
Allowance Collectively Evaluated for Impairment			576
Allowance Collectively Evaluated For Impairment, after ASU 2016-13	673
Loans Ending Balance			90,348
Total loans	91,394
Loans Individually Evaluated for Impairment			19
Loans Individually Evaluated For Impairment, after ASU 2016-13	86
Loans Collectively Evaluated for Impairment			90,329
Loans Collectively Evaluated For Impairment, after ASU 2016-13	91,308
Guaranteed student loans | Commercial and industrial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance			52	60	63	65
Allowance Ending Balance	13	112
Allowance Collectively Evaluated for Impairment			52
Allowance Collectively Evaluated For Impairment, after ASU 2016-13	13
Loans Ending Balance			20,617
Total loans	20,002
Loans Collectively Evaluated for Impairment			20,617
Loans Collectively Evaluated For Impairment, after ASU 2016-13	20,002
Consumer and other | Consumer real estate secured by 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance			97
Allowance Ending Balance	82
Allowance Individually Evaluated for Impairment			1
Allowance Collectively Evaluated for Impairment			96
Allowance Collectively Evaluated For Impairment, after ASU 2016-13	82
Loans Ending Balance			4,038
Total loans	4,383
Loans Individually Evaluated for Impairment			21
Loans Collectively Evaluated for Impairment			4,017
Loans Collectively Evaluated For Impairment, after ASU 2016-13	4,383
Consumer and other | Commercial and industrial loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance			37	$ 45	$ 35	$ 29
Allowance Ending Balance	35	$ 34
Loans Ending Balance			$ 4,038
Total loans	$ 4,383