Allowances for Loan Losses - Summary of Aging Analysis of the Recorded Investment of Past-Due Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Purchased Credit Impaired Loans	$ 5,385
Total Loans	668,672	$ 236,840
Total > 90 Days and Accruing	147	147
Agriculture Loans [Member]
Financing Receivable, Past Due [Line Items]
Purchased Credit Impaired Loans	0
Total Loans	8,873	11,246
Total > 90 Days and Accruing	0	0
Commercial Loans [Member]
Financing Receivable, Past Due [Line Items]
Purchased Credit Impaired Loans	1,918
Total Loans	123,536	21,534
Total > 90 Days and Accruing	0	0
Commercial Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Purchased Credit Impaired Loans	3,467
Total Loans	309,079	27,261
Total > 90 Days and Accruing	147	0
Residential Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Purchased Credit Impaired Loans	0
Total Loans	216,526	167,536
Total > 90 Days and Accruing	0	147
Consumer Loans [Member]
Financing Receivable, Past Due [Line Items]
Purchased Credit Impaired Loans	0
Total Loans	4,309	2,514
Total > 90 Days and Accruing	0	0
Municipal Loans [Member]
Financing Receivable, Past Due [Line Items]
Purchased Credit Impaired Loans	0
Total Loans	6,351	6,749
Total > 90 Days and Accruing	0	0
30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	3,443	2,851
30-59 Days Past Due [Member] | Agriculture Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	161	171
30-59 Days Past Due [Member] | Commercial Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	3	66
30-59 Days Past Due [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	2,112	1,297
30-59 Days Past Due [Member] | Residential Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	1,121	1,248
30-59 Days Past Due [Member] | Consumer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	46	69
30-59 Days Past Due [Member] | Municipal Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	0	0
60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	394	857
60-89 Days Past Due [Member] | Agriculture Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	0	0
60-89 Days Past Due [Member] | Commercial Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	0	0
60-89 Days Past Due [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	6	0
60-89 Days Past Due [Member] | Residential Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	387	831
60-89 Days Past Due [Member] | Consumer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	1	26
60-89 Days Past Due [Member] | Municipal Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	0	0
90 Days or Greater Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	147	344
90 Days or Greater Past Due [Member] | Agriculture Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	0	0
90 Days or Greater Past Due [Member] | Commercial Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	0	6
90 Days or Greater Past Due [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	147	0
90 Days or Greater Past Due [Member] | Residential Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	0	338
90 Days or Greater Past Due [Member] | Consumer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	0	0
90 Days or Greater Past Due [Member] | Municipal Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	0	0
Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	3,984	4,052
Total Past Due [Member] | Agriculture Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	161	171
Total Past Due [Member] | Commercial Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	3	72
Total Past Due [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	2,265	1,297
Total Past Due [Member] | Residential Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	1,508	2,417
Total Past Due [Member] | Consumer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	47	95
Total Past Due [Member] | Municipal Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	0	0
Current [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	659,303	232,788
Current [Member] | Agriculture Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	8,712	11,075
Current [Member] | Commercial Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	121,615	21,462
Current [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	303,347	25,964
Current [Member] | Residential Real Estate Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	215,018	165,119
Current [Member] | Consumer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	4,262	2,419
Current [Member] | Municipal Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, Gross	$ 6,351	$ 6,749