Income Tax Expense Benefit Continuing Operations Increase Decrease By Items Reconciliation [Abstract]

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operations attributable to deduction. Includes, but is not limited to, dividend deduction, deduction for dividend paid to employee stock ownership plan (ESOP), Medicare prescription drug benefit subsidy deduction, and other deductions.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax exempt income, equity in earnings (loss) of an unconsolidated subsidiary, minority noncontrolling interest income (loss), tax holiday, disposition of a business, disposition of an asset, repatriation of foreign earnings, repatriation of foreign earnings jobs creation act of 2004, increase (decrease) in enacted tax rate, prior year income taxes, increase (decrease) in deferred tax asset valuation allowance, and other adjustments.

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Income Taxes - Reconciliation of the Statutory Federal Income Tax Rate to the Effective Tax Rate (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Expense Benefit Continuing Operations Income Tax Reconciliation [Abstract]
Federal income tax at statutory rates									$ 5,294	$ 4,780	$ 3,832
(Decrease) increase resulting from:
State income tax, net of federal benefit									330	101	59
Tax exempt interest									(146)	(170)	(220)
Section 831 deduction									(266)	(268)	(236)
Other									(101)	(83)	(134)
Total Income Tax	$ 1,691	$ 1,287	$ 1,161	$ 972	$ 1,129	$ 959	$ 1,548	$ 724	$ 5,111	$ 4,360	$ 3,301