Allowances for Loan Losses - Summary of Impaired Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Financing Receivable, Impaired [Line Items]
With an allowance recorded, Recorded Investment					$ 0
With an allowance recorded, Unpaid Principal Balance					0
With an allowance recorded, Related Allowance	$ 18		$ 18		0
Total, Recorded Investment	5,687		5,687		751
Total, Unpaid Principal Balance	5,748		5,748		840
Total, Related Allowance	18		18		0
With no related allowance recorded, Average Recorded Investment	5,577	$ 138	5,744	$ 141
With no related allowance recorded, Interest Recognized	106	0	165	0
With an allowance recorded, Average Recorded Investment	176	0	177	0
With an allowance recorded, Interest Recognized	3	0	5	0
Total, Average Recorded Investment	5,753	138	5,921	141
Total, Interest Recognized	109		170
Agriculture Loans [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	100		100		0
With no related allowance recorded, Unpaid Principal Balance	100		100		0
With an allowance recorded, Recorded Investment					0
With an allowance recorded, Unpaid Principal Balance					0
With an allowance recorded, Related Allowance	0		0		0
Total, Recorded Investment	100		100		0
Total, Unpaid Principal Balance	100		100		0
Total, Related Allowance	0		0		0
With no related allowance recorded, Average Recorded Investment	133	0	210	0
With no related allowance recorded, Interest Recognized	5	0	8	0
With an allowance recorded, Average Recorded Investment	0	0	0	0
With an allowance recorded, Interest Recognized	0	0	0	0
Commercial Loans [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	35		35		42
With no related allowance recorded, Unpaid Principal Balance	55		55		61
With an allowance recorded, Recorded Investment					0
With an allowance recorded, Unpaid Principal Balance					0
With an allowance recorded, Related Allowance	0		0		0
Total, Recorded Investment	35		35		42
Total, Unpaid Principal Balance	55		55		61
Total, Related Allowance	0		0		0
With no related allowance recorded, Average Recorded Investment	37	0	35	0
With no related allowance recorded, Interest Recognized	0	0	0	0
With an allowance recorded, Average Recorded Investment	0		0	0
With an allowance recorded, Interest Recognized	0	0	0	0
Commercial Real Estate Loans [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	2,410		2,410		0
With no related allowance recorded, Unpaid Principal Balance	2,410		2,410		0
With an allowance recorded, Recorded Investment					0
With an allowance recorded, Unpaid Principal Balance					0
With an allowance recorded, Related Allowance	0		0		0
Total, Recorded Investment	2,410		2,410		0
Total, Unpaid Principal Balance	2,410		2,410		0
Total, Related Allowance	0		0		0
With no related allowance recorded, Average Recorded Investment	2,421	0	2,451	0
With no related allowance recorded, Interest Recognized	65	0	100	0
With an allowance recorded, Average Recorded Investment	0	0	0	0
With an allowance recorded, Interest Recognized	0	0	0	0
Residential Real Estate Loans [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	3,140		3,140		709
With no related allowance recorded, Unpaid Principal Balance	3,181		3,181		779
With an allowance recorded, Recorded Investment	174		174		0
With an allowance recorded, Unpaid Principal Balance	175		175		0
With an allowance recorded, Related Allowance	16		16		0
Total, Recorded Investment	2,966		2,966		709
Total, Unpaid Principal Balance	3,006		3,006		779
Total, Related Allowance	16		16		0
With no related allowance recorded, Average Recorded Investment	2,986	138	3,048	141
With no related allowance recorded, Interest Recognized	36		57
With an allowance recorded, Average Recorded Investment	174	0	175	0
With an allowance recorded, Interest Recognized	3	0	5	0
Consumer Loans [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment					0
With no related allowance recorded, Unpaid Principal Balance					0
With an allowance recorded, Recorded Investment	2		2		0
With an allowance recorded, Unpaid Principal Balance	2		2		0
With an allowance recorded, Related Allowance	2		2		0
Total, Recorded Investment	2		2		0
Total, Unpaid Principal Balance	2		2		0
Total, Related Allowance	2		2		0
With no related allowance recorded, Average Recorded Investment	0	0	0	0
With no related allowance recorded, Interest Recognized	0	0	0	0
With an allowance recorded, Average Recorded Investment	2	0	2	0
With an allowance recorded, Interest Recognized	0	0	0	0
Municipal Loans [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment					0
With no related allowance recorded, Unpaid Principal Balance					0
With an allowance recorded, Recorded Investment					0
With an allowance recorded, Unpaid Principal Balance					0
With an allowance recorded, Related Allowance	0		0		0
Total, Recorded Investment					0
Total, Unpaid Principal Balance					0
Total, Related Allowance	0		0		$ 0
With no related allowance recorded, Average Recorded Investment	0	0	0	0
With no related allowance recorded, Interest Recognized	0	0	0	0
With an allowance recorded, Average Recorded Investment	0	0	0	0
With an allowance recorded, Interest Recognized	$ 0	$ 0	$ 0	$ 0