Loans and allowance for loan losses - Loans evaluated for impairment (Details) - USD ($)
$ in Thousands
Mar. 31, 2021
Dec. 31, 2020
Mar. 31, 2020
Dec. 31, 2019
Financing Receivable, Allowance for Credit Losses [Line Items]        
Allowance Ending Balance $ 3,992 $ 3,970 $ 3,444 $ 3,186
Allowance Individually Evaluated for Impairment 8 17    
Allowance Collectively Evaluated for Impairment 3,984 3,953    
Loans Ending Balance 592,177 561,003    
Loans Individually Evaluated for Impairment 10,621 9,047    
Loans Collectively Evaluated for Impairment 581,556 551,956    
Construction and land development        
Financing Receivable, Allowance for Credit Losses [Line Items]        
Allowance Ending Balance 268 499 489 185
Allowance Collectively Evaluated for Impairment 268 499    
Loans Ending Balance 29,600 29,569    
Loans Collectively Evaluated for Impairment 29,600 29,569    
Commercial real estate        
Financing Receivable, Allowance for Credit Losses [Line Items]        
Allowance Ending Balance 2,224 2,517 1,986 1,589
Allowance Individually Evaluated for Impairment   9    
Allowance Collectively Evaluated for Impairment 2,224 2,508    
Loans Ending Balance 234,323 231,224    
Loans Individually Evaluated for Impairment 7,119 5,896    
Loans Collectively Evaluated for Impairment 227,204 225,328    
Consumer real estate        
Financing Receivable, Allowance for Credit Losses [Line Items]        
Allowance Ending Balance 228 269 273 678
Allowance Individually Evaluated for Impairment 8 8    
Allowance Collectively Evaluated for Impairment 220 261    
Loans Ending Balance 86,817 86,580    
Loans Individually Evaluated for Impairment 3,300 3,010    
Loans Collectively Evaluated for Impairment 83,517 83,570    
Residential [Member] | Construction and land development        
Financing Receivable, Allowance for Credit Losses [Line Items]        
Allowance Ending Balance 100 214 219 48
Allowance Collectively Evaluated for Impairment 100 214    
Loans Ending Balance 7,164 8,103    
Loans Collectively Evaluated for Impairment 7,164 8,103    
Commercial [Member] | Construction and land development        
Financing Receivable, Allowance for Credit Losses [Line Items]        
Allowance Ending Balance 168 285 270 137
Allowance Collectively Evaluated for Impairment 168 285    
Loans Ending Balance 22,436 21,466    
Loans Collectively Evaluated for Impairment 22,436 21,466    
Owner Occupied [Member] | Commercial real estate        
Financing Receivable, Allowance for Credit Losses [Line Items]        
Allowance Ending Balance 899 1,047 859 671
Allowance Individually Evaluated for Impairment   9    
Allowance Collectively Evaluated for Impairment 899 1,038    
Loans Ending Balance 99,677 99,784    
Loans Individually Evaluated for Impairment 5,224 3,905    
Loans Collectively Evaluated for Impairment 94,453 95,879    
Non-Owner Occupied [Member] | Commercial real estate        
Financing Receivable, Allowance for Credit Losses [Line Items]        
Allowance Ending Balance 1,286 1,421 1,058 831
Allowance Collectively Evaluated for Impairment 1,286 1,421    
Loans Ending Balance 125,202 121,184    
Loans Individually Evaluated for Impairment 1,895 1,991    
Loans Collectively Evaluated for Impairment 123,307 119,193    
Multifamily [Member] | Commercial real estate        
Financing Receivable, Allowance for Credit Losses [Line Items]        
Allowance Ending Balance 38 47 68 85
Allowance Collectively Evaluated for Impairment 38 47    
Loans Ending Balance 9,086 9,889    
Loans Collectively Evaluated for Impairment 9,086 9,889    
Farmland [Member] | Commercial real estate        
Financing Receivable, Allowance for Credit Losses [Line Items]        
Allowance Ending Balance 1 2 1 2
Allowance Collectively Evaluated for Impairment 1 2    
Loans Ending Balance 358 367    
Loans Collectively Evaluated for Impairment 358 367    
Home equity lines [Member] | Consumer real estate        
Financing Receivable, Allowance for Credit Losses [Line Items]        
Allowance Ending Balance 15 24 40 271
Allowance Collectively Evaluated for Impairment 15 24    
Loans Ending Balance 18,128 18,394    
Loans Individually Evaluated for Impairment 300 300    
Loans Collectively Evaluated for Impairment 17,828 18,094    
First Deed of Trust [Member] | Consumer real estate        
Financing Receivable, Allowance for Credit Losses [Line Items]        
Allowance Ending Balance 146 166 157 343
Allowance Individually Evaluated for Impairment 8 8    
Allowance Collectively Evaluated for Impairment 138 158    
Loans Ending Balance 58,028 57,089    
Loans Individually Evaluated for Impairment 2,258 2,011    
Loans Collectively Evaluated for Impairment 55,770 55,078    
Second Deed of Trust [Member] | Consumer real estate        
Financing Receivable, Allowance for Credit Losses [Line Items]        
Allowance Ending Balance 67 79 76 64
Allowance Collectively Evaluated for Impairment 67 79    
Loans Ending Balance 10,661 11,097    
Loans Individually Evaluated for Impairment 742 699    
Loans Collectively Evaluated for Impairment 9,919 10,398    
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 410 408 409 572
Allowance Collectively Evaluated for Impairment 410 408    
Loans Ending Balance 209,381 181,088    
Loans Individually Evaluated for Impairment 202 141    
Loans Collectively Evaluated for Impairment 209,179 180,947    
Guaranteed Student loans [Member] | Commercial and industrial loans        
Financing Receivable, Allowance for Credit Losses [Line Items]        
Allowance Ending Balance 76 87 104 108
Allowance Collectively Evaluated for Impairment 76 87    
Loans Ending Balance 29,062 29,657    
Loans Collectively Evaluated for Impairment 29,062 29,657    
Consumer And Other [Member]        
Financing Receivable, Allowance for Credit Losses [Line Items]        
Allowance Ending Balance 786 190    
Allowance Collectively Evaluated for Impairment 786 190    
Loans Ending Balance 2,994 2,885    
Loans Collectively Evaluated for Impairment 2,994 2,885    
Consumer And Other [Member] | Commercial and industrial loans        
Financing Receivable, Allowance for Credit Losses [Line Items]        
Allowance Ending Balance 38 36 $ 41 $ 30
Loans Ending Balance $ 2,994 $ 2,885