Income Taxes - Effective Tax Rates Differ from Statutory Federal Income Tax Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income taxes computed at the statutory federal tax rate	$ 3,524	$ 7,781	$ 8,343
Add (subtract) tax effect of:
Nontaxable interest income, net of nondeductible interest expense	(834)	(1,107)	(946)
Low income housing tax credit	(903)	(686)	(435)
Cash surrender value of BOLI	(143)	(201)	(197)
Nondeductible merger costs	1,034
Change in corporate tax rate		511
Other	(38)	62	(146)
Income tax expense	$ 2,640	$ 6,360	$ 6,619

Income Tax Effect Of Additions subtractions [Abstract]

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Income Tax Reconciliation Bank Owned Life Insurance Income

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Income Tax Reconciliation Low Income Housing Tax Credit

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Income Tax Reconciliation Nontaxable Interest Income Net Of Nondeductible Interest Expense

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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 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 increase (decrease) in the income tax rates.

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