Fair Value - Schedule of Quantitative Information about Nonrecurring Level 3 Fair Value Measurements (Detail) $ in Thousands	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	$ 85	$ 148
Appraisals [Member] | Measurement Input, Discount Rate [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rates	10	10
Appraisals [Member] | Measurement Input, Discount Rate [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rates	20	20