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Loans (Impaired Loans) - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) Contract	Dec. 31, 2018 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Additional funds available to be advanced in connection with impaired loans	$ 4
Impaired loans classified as troubled debt restructured	$ 956	$ 178
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	120 days
Delinquent period for charging down commercial and agricultural credits	120 days
Foreclosed residential real estate property	$ 214	$ 600
Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of contracts modified | Contract	1
Foreclosed residential real estate property	$ 50	61
Residential real estate properties foreclosure proceedings	$ 383	$ 278
Principal Forgiveness [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of contracts modified | Contract	0
Payment Changes to Interest Only for Extended Maturity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of contracts modified | Contract	4
Lowering of Payment to Match Extended Maturity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of contracts modified | Contract	1

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Unsecured consumer loans credit card credits and overdraft.

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Recorded investment of consumer mortgage loan receivables secured by residential real estate properties for which formal foreclosure proceedings are in process.

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Carrying amount as of the balance sheet date of land and buildings obtained through foreclosure proceedings or defeasance in full or partial satisfaction of a debt arrangement.

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