Loans - Loans Individually Evaluated for Impairment by Portfolio Class of Loans (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	$ 5,680	$ 1,228	$ 3,063	$ 5,680	$ 3,063	$ 1,228
With a specific allowance recorded, Recorded Investment	4,989	10,711	8,976	4,989	8,976	10,711
Related Allowance	2,419	2,184	1,156	2,419	1,156	2,184
Recorded Investment	10,669	11,939	12,039	10,669	12,039	11,939
Average Recorded Investment	9,748	11,676	12,206	11,258	12,836	12,247
Consumer Real Estate [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	657	604	770	657	770	604
With no related allowance recorded, Unpaid Principal Balance	657	604	823	657	823	604
With no related allowance recorded, Average Recorded Investment	390		494	381	501	456
With no related allowance recorded, Interest Income Recognized	1		1	2	3	5
With no related allowance recorded, Interest Income Recognized Cash Basis	4		3	6	7	15
With a specific allowance recorded, Average Recorded Investment			55		117	59
Recorded Investment	657	604	770	657	770	604
Unpaid Principal Balance	657	604	823	657	823	604
Average Recorded Investment	390		549	381	618	515
Interest Income Recognized	1		1	2	3	5
Interest Income Recognized Cash Basis	4		3	6	7	15
Agricultural Real Estate [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	2,414	423	728	2,414	728	423
With no related allowance recorded, Unpaid Principal Balance	2,518	423	728	2,518	728	423
With no related allowance recorded, Average Recorded Investment	2,247		994	1,696	1,262	1,000
With no related allowance recorded, Interest Income Recognized	6		22	13	44
With no related allowance recorded, Interest Income Recognized Cash Basis	3			5
With a specific allowance recorded, Recorded Investment		6,302	5,794		5,794	6,302
With a specific allowance recorded, Unpaid Principal Balance		6,406	5,794		5,794	6,406
Related Allowance		691	914		914	691
With a specific allowance recorded, Average Recorded Investment			5,556	2,775	5,357	5,414
With a specific allowance recorded, Interest Income Recognized						54
Recorded Investment	2,414	6,725	6,522	2,414	6,522	6,725
Unpaid Principal Balance	2,518	6,829	6,522	2,518	6,522	6,829
Average Recorded Investment	2,247		6,550	4,471	6,619	6,414
Interest Income Recognized	6		22	13	44	87
Interest Income Recognized Cash Basis	3			5
With no related allowance recorded, Adjusted Interest Income Recognized						33
Agricultural [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	1,296		131	1,296	131
With no related allowance recorded, Unpaid Principal Balance	1,296		231	1,296	231
With no related allowance recorded, Average Recorded Investment	445		184	233	176	143
With no related allowance recorded, Interest Income Recognized			4		6	18
With no related allowance recorded, Interest Income Recognized Cash Basis	1			1		3
With a specific allowance recorded, Recorded Investment		20	117		117	20
With a specific allowance recorded, Unpaid Principal Balance		20	117		117	20
Related Allowance		1	117		117	1
With a specific allowance recorded, Average Recorded Investment			39		127	94
Recorded Investment	1,296	20	248	1,296	248	20
Unpaid Principal Balance	1,296	20	348	1,296	348	20
Average Recorded Investment	445		223	233	303	237
Interest Income Recognized			4		6	18
Interest Income Recognized Cash Basis	1			1		3
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	1,148	180	181	1,148	181	180
With no related allowance recorded, Unpaid Principal Balance	1,148	180	181	1,148	181	180
With no related allowance recorded, Average Recorded Investment	1,323		480	991	1,393	1,445
With no related allowance recorded, Interest Income Recognized	7		4	11	8	70
With no related allowance recorded, Interest Income Recognized Cash Basis	14		3	19	6	9
With a specific allowance recorded, Recorded Investment	2,985	3,381	3,065	2,985	3,065	3,381
With a specific allowance recorded, Unpaid Principal Balance	2,985	3,381	3,065	2,985	3,065	3,381
Related Allowance	573	664	125	573	125	664
With a specific allowance recorded, Average Recorded Investment	3,105		3,087	3,426	2,002	2,199
With a specific allowance recorded, Interest Income Recognized	38		27	74	54	70
With a specific allowance recorded, Interest Income Recognized Cash Basis			3		3	3
Recorded Investment	4,133	3,561	3,246	4,133	3,246	3,561
Unpaid Principal Balance	4,133	3,561	3,246	4,133	3,246	3,561
Average Recorded Investment	4,428		3,567	4,417	3,395	3,644
Interest Income Recognized	45		31	85	62	140
Interest Income Recognized Cash Basis	14		6	19	9	12
Commercial and Industrial [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	145	21	1,236	145	1,236	21
With no related allowance recorded, Unpaid Principal Balance	145	21	1,367	145	1,367	21
With no related allowance recorded, Average Recorded Investment	207		1,298	231	1,546	920
With no related allowance recorded, Interest Income Recognized			6	2	23	24
With no related allowance recorded, Interest Income Recognized Cash Basis	10		2	10	3	158
With a specific allowance recorded, Recorded Investment	2,004	982		2,004		982
With a specific allowance recorded, Unpaid Principal Balance	2,004	982		2,004		982
Related Allowance	1,846	825		1,846		825
With a specific allowance recorded, Average Recorded Investment	2,011			1,502	335	498
With a specific allowance recorded, Interest Income Recognized	52			65		17
Recorded Investment	2,149	1,003	1,236	2,149	1,236	1,003
Unpaid Principal Balance	2,149	1,003	1,367	2,149	1,367	1,003
Average Recorded Investment	2,218		1,298	1,733	1,881	1,418
Interest Income Recognized	52		6	67	23	41
Interest Income Recognized Cash Basis	10		2	10	3	158
Consumer [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	20		17	20	17
With no related allowance recorded, Unpaid Principal Balance	20		27	20	27
With no related allowance recorded, Average Recorded Investment	20		19	19	20	17
With no related allowance recorded, Interest Income Recognized				1
With a specific allowance recorded, Recorded Investment		26				26
With a specific allowance recorded, Unpaid Principal Balance		26				26
Related Allowance		3				3
With a specific allowance recorded, Average Recorded Investment				4		2
With a specific allowance recorded, Interest Income Recognized						1
Recorded Investment	20	26	17	20	17	26
Unpaid Principal Balance	20	$ 26	27	20	27	26
Average Recorded Investment	$ 20		$ 19	23	$ 20	19
Interest Income Recognized				$ 1		$ 1

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
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- Definition

Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

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Amount of allowance for credit losses related to recorded investment.

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Amount of interest income, recognized on accrual basis, on financing receivables, for which there is a related allowance for credit losses and are recognized as impaired.

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