Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Summary Of Significant Accounting Policies [Line Items]
Interest bearing amounts held at other financial institutions	$ 43,100,000	$ 29,300,000
Days loan should be past due after contractual due date to be considered as delinquent loan	30 days
Days in which collection of interest or principal should be past to be placed on non-accrual status	90 days
Goodwill impairment	$ 0	0	$ 0
Impairment of intangible assets	0	0	0
Indefinite lived intangible assets	0
Impairment charges	$ 0	$ 0	$ 0
Dilutive effect of common stock issuable upon exercise of options	205,959	310,614	435,800
Anti-dilutive shares	198,671	114,130	125,765
Maximum [Member] | Premises [Member]
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, depreciation period	40 years
Maximum [Member] | Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, depreciation period	20 years
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Tax benefit, Percentage	50.00%
Minimum [Member] | Premises [Member]
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, depreciation period	15 years
Minimum [Member] | Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, depreciation period	3 years