Loans (Impaired Loans) - Additional Information (Detail)	3 Months Ended				9 Months Ended
	Sep. 30, 2024 USD ($) Loan	Mar. 31, 2024 Contract	Sep. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) Loan Contract	Sep. 30, 2023 USD ($) Loan	Dec. 31, 2023 USD ($)	Jan. 01, 2023 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Modifications to borrower experiencing financial difficulty	$ 0		$ 0
Maximum time for re-evaluation (in months)					12 months
Re-evaluation period for real estate					2 years
Unsecured consumer loans, credit card credits and overdraft lines of credit reach					90 days
Delinquent period for charging down consumer loans					90 days
Litigation and any deficiency charged off period					150 days
Delinquent period for charging down/allocated commercial and agricultural credits					120 days
Number of contracts modified	0	1			0	1
Increase to loan balance				$ 411,000
Additional funds advanced with imapired loans				$ 0
Principal Forgiveness [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of contracts modified | Contract					0
Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Foreclosed residential real estate property	$ 0		0		$ 0	$ 0	$ 0
Residential real estate properties foreclosure proceedings	$ 755,000		$ 92,000		$ 755,000	$ 92,000	$ 679,000
ASU 2016-13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses on loans and unfunded commitments								$ 4,500,000
Allowance for credit losses on loans and unfunded commitments net of tax								$ 3,400,000