Loans and Allowance for Credit Losses - Impaired Loans, Segregated by Class of Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Financing Receivable Impaired [Line Items]
With no related allowance recorded, Unpaid Principal Balance	$ 5,608	$ 10,562
With no related allowance recorded, Recorded Investment	5,082	4,324
With no related allowance recorded, Average Recorded Investment	6,058	3,312
With no related allowance recorded, Interest Income Recognized	245	59
With related allowance recorded, Unpaid Principal Balance	29,796	26,742
With related allowance recorded, Recorded Investment	21,968	20,702
With an allowance recorded, Allowance for Credit Losses Allocated	4,599	4,167
With an allowance recorded, Average Recorded Investment	20,769	15,403
With an allowance recorded, Interest Income Recognized	347	461
Unpaid Principal Balance	35,404	37,304
Recorded Investment	27,050	25,026
Average Recorded Investment	26,827	18,715
Interest Income Recognized	592	520
Commercial Real Estate [Member]
Financing Receivable Impaired [Line Items]
With no related allowance recorded, Unpaid Principal Balance	3,068	3,948
With no related allowance recorded, Recorded Investment	3,068	3,376
With no related allowance recorded, Average Recorded Investment	3,542	2,117
With no related allowance recorded, Interest Income Recognized	104	53
With related allowance recorded, Unpaid Principal Balance	4,719	2,297
With related allowance recorded, Recorded Investment	4,390	2,071
With an allowance recorded, Allowance for Credit Losses Allocated	1,015	455
With an allowance recorded, Average Recorded Investment	3,382	1,214
With an allowance recorded, Interest Income Recognized	105	37
Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
With no related allowance recorded, Unpaid Principal Balance	0	2,925
With no related allowance recorded, Average Recorded Investment	398	251
With no related allowance recorded, Interest Income Recognized	0	1
With related allowance recorded, Unpaid Principal Balance	12,424	8,452
With related allowance recorded, Recorded Investment	7,798	5,041
With an allowance recorded, Allowance for Credit Losses Allocated	1,482	1,335
With an allowance recorded, Average Recorded Investment	6,760	5,059
With an allowance recorded, Interest Income Recognized	164	249
Residential Real Estate [Member]
Financing Receivable Impaired [Line Items]
With no related allowance recorded, Unpaid Principal Balance	19	21
With no related allowance recorded, Average Recorded Investment		5
With no related allowance recorded, Interest Income Recognized	1	1
With related allowance recorded, Unpaid Principal Balance	5,260	7,605
With related allowance recorded, Recorded Investment	4,670	7,251
With an allowance recorded, Allowance for Credit Losses Allocated	1,145	1,086
With an allowance recorded, Average Recorded Investment	5,011	3,912
With an allowance recorded, Interest Income Recognized	40	156
Agricultural Real Estate [Member]
Financing Receivable Impaired [Line Items]
With no related allowance recorded, Unpaid Principal Balance	2,490	1,342
With no related allowance recorded, Recorded Investment	2,014	948
With no related allowance recorded, Average Recorded Investment	2,009	939
With no related allowance recorded, Interest Income Recognized	140
With related allowance recorded, Unpaid Principal Balance	5,594	4,753
With related allowance recorded, Recorded Investment	3,737	3,266
With an allowance recorded, Allowance for Credit Losses Allocated	697	660
With an allowance recorded, Average Recorded Investment	3,520	1,950
With an allowance recorded, Interest Income Recognized	10	1
Consumer [Member]
Financing Receivable Impaired [Line Items]
With no related allowance recorded, Unpaid Principal Balance	31	23
With no related allowance recorded, Interest Income Recognized		1
With related allowance recorded, Unpaid Principal Balance	846	689
With related allowance recorded, Recorded Investment	781	603
With an allowance recorded, Allowance for Credit Losses Allocated	187	150
With an allowance recorded, Average Recorded Investment	706	477
With an allowance recorded, Interest Income Recognized	22	17
Agricultural [Member]
Financing Receivable Impaired [Line Items]
With no related allowance recorded, Unpaid Principal Balance	0	2,303
With no related allowance recorded, Average Recorded Investment	109
With no related allowance recorded, Interest Income Recognized		3
With related allowance recorded, Unpaid Principal Balance	953	2,946
With related allowance recorded, Recorded Investment	592	2,470
With an allowance recorded, Allowance for Credit Losses Allocated	73	481
With an allowance recorded, Average Recorded Investment	1,390	2,791
With an allowance recorded, Interest Income Recognized	$ 6	$ 1