Loans and Allowance for Credit Losses - Impaired Loans, Segregated by Class of Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Financing Receivable Impaired [Line Items]
With no related allowance recorded, Unpaid Principal Balance	$ 4,042	$ 8,513
With no related allowance recorded, Recorded Investment	2,474	4,102
With no related allowance recorded, Average Recorded Investment	4,465	4,896
With no related allowance recorded, Interest Income Recognized	176	192
With related allowance recorded, Unpaid Principal Balance	23,897	30,712
With related allowance recorded, Recorded Investment	15,127	25,259
With an allowance recorded, Allowance for Credit Losses Allocated	4,244	7,338
With an allowance recorded, Average Recorded Investment	17,464	45,573
With an allowance recorded, Interest Income Recognized	224	356
Unpaid Principal Balance	27,939	39,225
Recorded Investment	17,601	29,361
Average Recorded Investment	21,929	50,469
Interest Income Recognized	400	548
Commercial Real Estate [Member]
Financing Receivable Impaired [Line Items]
With no related allowance recorded, Unpaid Principal Balance	2,443
With no related allowance recorded, Recorded Investment	1,866
With no related allowance recorded, Average Recorded Investment	1,595	336
With no related allowance recorded, Interest Income Recognized		3
With related allowance recorded, Unpaid Principal Balance	1,011	7,690
With related allowance recorded, Recorded Investment	823	6,833
With an allowance recorded, Allowance for Credit Losses Allocated	206	1,632
With an allowance recorded, Average Recorded Investment	3,126	6,985
With an allowance recorded, Interest Income Recognized	10	19
Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
With no related allowance recorded, Unpaid Principal Balance	21	6,060
With no related allowance recorded, Recorded Investment		1,964
With no related allowance recorded, Average Recorded Investment	1,184	521
With no related allowance recorded, Interest Income Recognized		101
With related allowance recorded, Unpaid Principal Balance	10,758	4,976
With related allowance recorded, Recorded Investment	5,838	4,593
With an allowance recorded, Allowance for Credit Losses Allocated	1,091	1,800
With an allowance recorded, Average Recorded Investment	4,214	25,881
With an allowance recorded, Interest Income Recognized	170	119
Residential Real Estate [Member]
Financing Receivable Impaired [Line Items]
With no related allowance recorded, Unpaid Principal Balance	54	609
With no related allowance recorded, Recorded Investment	25	429
With no related allowance recorded, Average Recorded Investment	312	126
With no related allowance recorded, Interest Income Recognized	6	4
With related allowance recorded, Unpaid Principal Balance	3,488	5,170
With related allowance recorded, Recorded Investment	3,181	4,646
With an allowance recorded, Allowance for Credit Losses Allocated	786	888
With an allowance recorded, Average Recorded Investment	3,483	3,204
With an allowance recorded, Interest Income Recognized	27	41
Agricultural Real Estate [Member]
Financing Receivable Impaired [Line Items]
With no related allowance recorded, Unpaid Principal Balance	1,518	1,795
With no related allowance recorded, Recorded Investment	583	1,660
With no related allowance recorded, Average Recorded Investment	1,360	2,178
With no related allowance recorded, Interest Income Recognized	169	82
With related allowance recorded, Unpaid Principal Balance	1,956	3,726
With related allowance recorded, Recorded Investment	1,469	2,738
With an allowance recorded, Allowance for Credit Losses Allocated	216	637
With an allowance recorded, Average Recorded Investment	2,095	3,224
With an allowance recorded, Interest Income Recognized	7	56
Consumer [Member]
Financing Receivable Impaired [Line Items]
With no related allowance recorded, Unpaid Principal Balance	6	49
With no related allowance recorded, Recorded Investment		49
With no related allowance recorded, Average Recorded Investment	12	10
With no related allowance recorded, Interest Income Recognized		2
With related allowance recorded, Unpaid Principal Balance	412	314
With related allowance recorded, Recorded Investment	348	274
With an allowance recorded, Allowance for Credit Losses Allocated	85	74
With an allowance recorded, Average Recorded Investment	302	251
With an allowance recorded, Interest Income Recognized	8	8
Agricultural [Member]
Financing Receivable Impaired [Line Items]
With no related allowance recorded, Average Recorded Investment	2	1,725
With no related allowance recorded, Interest Income Recognized	1
With related allowance recorded, Unpaid Principal Balance	6,272	8,836
With related allowance recorded, Recorded Investment	3,468	6,175
With an allowance recorded, Allowance for Credit Losses Allocated	1,860	2,307
With an allowance recorded, Average Recorded Investment	4,244	6,028
With an allowance recorded, Interest Income Recognized	$ 2	$ 113