Allowances for Loan Losses - Summary of Allowances for Loan Losses by Loan Class (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Loans and Leases Receivable Disclosure [Line Items]
Beginning balance	$ 3,890	$ 2,875	$ 3,152	$ 2,789
Charge-offs	0	(2)	(2)	(49)
Recoveries	164	5	229	47
Provision	515	457	1,190	548
Ending balance	4,569	3,335	4,569	3,335
Agriculture Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Beginning balance	17	98	23	120
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision	(21)	(31)	(15)	(9)
Ending balance	38	129	38	129
Commercial and PPP Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Beginning balance	506	350	582	290
Charge-offs	0	0	(1)	0
Recoveries	25	1	32	19
Provision	96	107	(14)	149
Ending balance	627	458	627	458
Commercial Real Estate Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Beginning balance	1,786	342	799	314
Charge-offs	0	0	(1)	0
Recoveries	0	0	0	0
Provision	427	21	1,415	49
Ending balance	2,213	363	2,213	363
Residential Real Estate Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Beginning balance	1,547	1,670	1,634	1,702
Charge-offs	0	(2)	0	(49)
Recoveries	139	4	195	28
Provision	(43)	(698)	(186)	(689)
Ending balance	1,643	2,370	1,643	2,370
Consumer Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Beginning balance	21	23	22	35
Charge-offs	0	0	0	0
Recoveries	0	0	2	0
Provision	12	(3)	(9)	(15)
Ending balance	33	20	33	20
Municipal Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Beginning balance	13	16	15	18
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision	(2)	(13)	(0)	(11)
Ending balance	15	29	15	29
Unallocated [Member]
Loans and Leases Receivable Disclosure [Line Items]
Beginning balance	0	376	77	310
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision	(0)	410	(77)	344
Ending balance	$ 0	$ 34	$ 0	$ 34