Loans - Summary of Activities in Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025	Dec. 31, 2025
Allowance for Loan Losses
Balance at beginning of year	$ 27,941	$ 26,977	$ 27,688	$ 25,826	$ 25,826
Provision for (recovery of) credit losses - loans	(104)	557	371	2,029	2,596
Charge Offs	(135)	(120)	(542)	(587)	(1,028)
Recoveries	100	61	285	207	294
Balance at ending of year	27,802	27,475	27,802	27,475	27,688
Consumer Real Estate [Member]
Allowance for Loan Losses
Balance at beginning of year	5,053	3,653	4,266	3,543	3,543
Provision for (recovery of) credit losses - loans	203	474	989	582	738
Charge Offs	(41)		(44)		(20)
Recoveries	3	2	7	4	5
Balance at ending of year	5,218	4,129	5,218	4,129	4,266
Agricultural Real Estate [Member]
Allowance for Loan Losses
Balance at beginning of year	946	738	735	895	895
Provision for (recovery of) credit losses - loans	(141)	18	70	(139)	(160)
Balance at ending of year	805	756	805	756	735
Agricultural [Member]
Allowance for Loan Losses
Balance at beginning of year	866	334	474	285	285
Provision for (recovery of) credit losses - loans	(28)	82	312	121	179
Recoveries			52	10	10
Balance at ending of year	838	416	838	416	474
Commercial Real Estate [Member]
Allowance for Loan Losses
Balance at beginning of year	15,894	17,354	17,428	16,560	16,560
Provision for (recovery of) credit losses - loans	44	(455)	(1,495)	320	844
Charge Offs		0
Recoveries	2	2	7	21	24
Balance at ending of year	15,940	16,901	15,940	16,901	17,428
Commercial and Industrial [Member]
Allowance for Loan Losses
Balance at beginning of year	3,500	3,376	3,286	2,969	2,969
Provision for (recovery of) credit losses - loans	(38)	366	212	786	533
Charge Offs		(1)	(39)	(26)	(250)
Recoveries	1	9	4	21	34
Balance at ending of year	3,463	3,750	3,463	3,750	3,286
Consumer [Member]
Allowance for Loan Losses
Balance at beginning of year	1,147	945	953	1,012	1,012
Provision for (recovery of) credit losses - loans	(106)	95	332	367	478
Charge Offs	(94)	(119)	(459)	(561)	(758)
Recoveries	94	48	215	151	221
Balance at ending of year	1,041	969	1,041	969	953
Other [Member]
Allowance for Loan Losses
Balance at beginning of year	535	577	546	562	562
Provision for (recovery of) credit losses - loans	(38)	(23)	(49)	(8)	(16)
Balance at ending of year	$ 497	$ 554	$ 497	$ 554	$ 546

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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