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Loans (Impaired Loans) - Additional Information (Detail)	1 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($) Loan	May 31, 2020 Loan	Jun. 30, 2021 USD ($) Contract Loan	Jun. 30, 2020 USD ($) Loan	Jun. 30, 2021 USD ($) Contract Loan	Jun. 30, 2020 USD ($) Contract Loan	Dec. 31, 2020 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Additional funds available to be advanced in connection with impaired loans	$ 5,700		$ 5,700		$ 5,700
Impaired loans classified as troubled debt restructured	$ 5,500,000		$ 5,500,000	$ 6,400,000	$ 5,500,000	$ 6,400,000	$ 6,500,000
Number of contracts modified | Loan			1	3		5
TDR impaired loans paid off | Loan	2	1
TDR loans, subsequently defaulted during the period			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
Delinquent period for charging down commercial and agricultural credits					120 days
Foreclosed residential real estate property	$ 198,000		$ 198,000		$ 198,000		71,000
Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Litigation and any deficiency charged off period					150 days
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired loans classified as troubled debt restructured	86,000		$ 86,000	$ 481,000	$ 86,000	$ 481,000
Number of contracts modified | Contract			1		1	2
TDR impaired loans paid off | Loan					1	1
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired loans classified as troubled debt restructured	480,000		$ 480,000		$ 480,000
TDR impaired loans paid off | Loan					1
TDR impaired loans charged off | Loan					3
TDR impaired loans charged off amount					$ 809,000
Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Foreclosed residential real estate property	198,000		198,000	0	198,000	$ 0	71,000
Residential real estate properties foreclosure proceedings	$ 100,000		$ 100,000	$ 854,000	$ 100,000	$ 854,000	$ 910,000
Principal Forgiveness [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of contracts modified | Contract					0

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