Loans - Summary of Activities in Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Allowance for Loan Losses
Balance at beginning of year	$ 26,977	$ 25,270	$ 25,826	$ 25,024	$ 25,024
Provision for (recovery of) credit losses - loans	557	282	2,029	598	944
Charge Offs	(120)	(123)	(587)	(400)	(480)
Recoveries	61	55	207	262	338
Balance at ending of year	27,475	25,484	27,475	25,484	25,826
Consumer Real Estate [Member]
Allowance for Loan Losses
Balance at beginning of year	3,653	3,201	3,543	3,581	3,581
Provision for (recovery of) credit losses - loans	474	161	582	(211)	(31)
Charge Offs				(13)	(13)
Recoveries	2	1	4	6	6
Balance at ending of year	4,129	3,363	4,129	3,363	3,543
Agricultural Real Estate [Member]
Allowance for Loan Losses
Balance at beginning of year	738	926	895	312	312
Provision for (recovery of) credit losses - loans	18	11	(139)	625	583
Balance at ending of year	756	937	756	937	895
Agricultural [Member]
Allowance for Loan Losses
Balance at beginning of year	334	285	285	336	336
Provision for (recovery of) credit losses - loans	82	(24)	121	(75)	(52)
Recoveries			10		1
Balance at ending of year	416	261	416	261	285
Commercial Real Estate [Member]
Allowance for Loan Losses
Balance at beginning of year	17,354	16,319	16,560	17,400	17,400
Provision for (recovery of) credit losses - loans	(455)	148	320	(937)	(834)
Charge Offs		(15)		(15)	(15)
Recoveries	2	3	21	7	9
Balance at ending of year	16,901	16,455	16,901	16,455	16,560
Commercial and Industrial [Member]
Allowance for Loan Losses
Balance at beginning of year	3,376	2,801	2,969	1,766	1,766
Provision for (recovery of) credit losses - loans	366	17	786	1,048	1,176
Charge Offs	(1)	(5)	(26)	(106)	(106)
Recoveries	9	22	21	127	133
Balance at ending of year	3,750	2,835	3,750	2,835	2,969
Consumer [Member]
Allowance for Loan Losses
Balance at beginning of year	945	1,172	1,012	1,302	1,302
Provision for (recovery of) credit losses - loans	95	(12)	367	(72)	(133)
Charge Offs	(119)	(103)	(561)	(266)	(346)
Recoveries	48	29	151	122	189
Balance at ending of year	969	1,086	969	1,086	1,012
Other [Member]
Allowance for Loan Losses
Balance at beginning of year	577	566	562	327	327
Provision for (recovery of) credit losses - loans	(23)	(19)	(8)	220	235
Balance at ending of year	$ 554	$ 547	$ 554	$ 547	$ 562

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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Amount of increase in allowance for credit loss on financing receivable from recovery.

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