Allowances for Loan Losses - Summary of Aging Analysis of the Recorded Investment of Past-Due Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Purchased Credit Impaired Loans	$ 5,564	$ 5,556
Loans receivable	731,080	715,039
Total > 90 Days and Accruing	0	762
Agriculture Loans [Member]
Financing Receivable, Past Due [Line Items]
Purchased Credit Impaired Loans
Loans receivable	8,111	9,341
Total > 90 Days and Accruing	0
Commercial and PPP Loans [Member]
Financing Receivable, Past Due [Line Items]
Purchased Credit Impaired Loans	641	512
Loans receivable	104,700	122,378
Total > 90 Days and Accruing	0
Commercial Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Purchased Credit Impaired Loans	4,329	4,394
Loans receivable	353,559	338,749
Total > 90 Days and Accruing	0
Residential Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Purchased Credit Impaired Loans	594	650
Loans receivable	252,158	231,302
Total > 90 Days and Accruing	0	762
Consumer Loans [Member]
Financing Receivable, Past Due [Line Items]
Purchased Credit Impaired Loans
Loans receivable	6,359	7,087
Total > 90 Days and Accruing	0
Municipal Loans [Member]
Financing Receivable, Past Due [Line Items]
Purchased Credit Impaired Loans
Loans receivable	6,193	6,182
Total > 90 Days and Accruing	0
30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	2,479	1,852
30-59 Days Past Due [Member] | Agriculture Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	187	83
30-59 Days Past Due [Member] | Commercial and PPP Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	33	66
30-59 Days Past Due [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross		245
30-59 Days Past Due [Member] | Residential Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	2,240	1,427
30-59 Days Past Due [Member] | Consumer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	19	31
30-59 Days Past Due [Member] | Municipal Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross
60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	26	213
60-89 Days Past Due [Member] | Agriculture Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross
60-89 Days Past Due [Member] | Commercial and PPP Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross
60-89 Days Past Due [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross
60-89 Days Past Due [Member] | Residential Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	25	211
60-89 Days Past Due [Member] | Consumer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	1	2
60-89 Days Past Due [Member] | Municipal Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross
90 Days or Greater Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	516	869
90 Days or Greater Past Due [Member] | Agriculture Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross
90 Days or Greater Past Due [Member] | Commercial and PPP Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross
90 Days or Greater Past Due [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross
90 Days or Greater Past Due [Member] | Residential Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	516	869
90 Days or Greater Past Due [Member] | Consumer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross
90 Days or Greater Past Due [Member] | Municipal Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross
Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	3,021	2,934
Total Past Due [Member] | Agriculture Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	187	83
Total Past Due [Member] | Commercial and PPP Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	33	66
Total Past Due [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross		245
Total Past Due [Member] | Residential Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	2,781	2,507
Total Past Due [Member] | Consumer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	20	33
Total Past Due [Member] | Municipal Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross
Current [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	722,495	706,549
Current [Member] | Agriculture Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	7,924	9,258
Current [Member] | Commercial and PPP Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	104,026	121,800
Current [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	349,230	334,110
Current [Member] | Residential Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	248,783	228,145
Current [Member] | Consumer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	6,339	7,054
Current [Member] | Municipal Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	$ 6,193	$ 6,182