Loans - Summary of Activities in Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Allowance for Loan Losses
Balance at beginning of year	$ 25,270	$ 24,910	$ 25,024	$ 20,313	$ 20,313
Provision for credit losses - loans	282	460	598	1,420	1,698
Charge Offs	(123)	(148)	(400)	(330)	(990)
Recoveries	55	55	262	310	439
Balance at ending of year	25,484	25,277	25,484	25,277	25,024
Consumer Real Estate [Member]
Allowance for Loan Losses
Balance at beginning of year	3,201	3,998	3,581	998	998
Provision for credit losses - loans	161	(170)	(211)	(57)	(326)
Charge Offs			(13)
Recoveries	1	14	6	27	35
Balance at ending of year	3,363	3,842	3,363	3,842	3,581
Agricultural Real Estate [Member]
Allowance for Loan Losses
Balance at beginning of year	926	237	312	349	349
Provision for credit losses - loans	11	77	625	27	24
Recoveries		1		105	105
Balance at ending of year	937	315	937	315	312
Agricultural [Member]
Allowance for Loan Losses
Balance at beginning of year	285	107	336	751	751
Provision for credit losses - loans	(24)	78	(75)	84	225
Recoveries					10
Balance at ending of year	261	185	261	185	336
Commercial Real Estate [Member]
Allowance for Loan Losses
Balance at beginning of year	16,319	16,681	17,400	11,924	11,924
Provision for credit losses - loans	148	123	(937)	1,374	1,967
Charge Offs	(15)		(15)
Recoveries	3	1	7	6	8
Balance at ending of year	16,455	16,805	16,455	16,805	17,400
Commercial and Industrial [Member]
Allowance for Loan Losses
Balance at beginning of year	3,367	2,767	2,093	5,382	5,382
Provision for credit losses - loans	(2)	(65)	1,268	(527)	(643)
Charge Offs	(5)		(106)		(565)
Recoveries	22	6	127	18	84
Balance at ending of year	3,382	2,708	3,382	2,708	2,093
Consumer [Member]
Allowance for Loan Losses
Balance at beginning of year	1,172	1,120	1,302	909	909
Provision for credit losses - loans	(12)	417	(72)	519	451
Charge Offs	(103)	(148)	(266)	(330)	(425)
Recoveries	29	33	122	154	197
Balance at ending of year	$ 1,086	1,422	$ 1,086	1,422	1,302
Cumulative Effect, Period of Adoption, Adjustment [Member]
Allowance for Loan Losses
Balance at beginning of year				$ 3,564	$ 3,564
Accounting Standards Update [Extensible Enumeration]				Accounting Standards Update 2016-13 [Member]	Accounting Standards Update 2016-13 [Member]
Cumulative Effect, Period of Adoption, Adjustment [Member] | Consumer Real Estate [Member]
Allowance for Loan Losses
Balance at beginning of year				$ 2,874	$ 2,874
Balance at ending of year		2,874		2,874
Cumulative Effect, Period of Adoption, Adjustment [Member] | Agricultural Real Estate [Member]
Allowance for Loan Losses
Balance at beginning of year				(166)	(166)
Balance at ending of year		(166)		(166)
Cumulative Effect, Period of Adoption, Adjustment [Member] | Agricultural [Member]
Allowance for Loan Losses
Balance at beginning of year				(650)	(650)
Balance at ending of year		(650)		(650)
Cumulative Effect, Period of Adoption, Adjustment [Member] | Commercial Real Estate [Member]
Allowance for Loan Losses
Balance at beginning of year				3,501	3,501
Balance at ending of year		3,501		3,501
Cumulative Effect, Period of Adoption, Adjustment [Member] | Commercial and Industrial [Member]
Allowance for Loan Losses
Balance at beginning of year				(2,165)	(2,165)
Balance at ending of year		(2,165)		(2,165)
Cumulative Effect, Period of Adoption, Adjustment [Member] | Consumer [Member]
Allowance for Loan Losses
Balance at beginning of year				170	$ 170
Balance at ending of year		$ 170		$ 170