Fair Value Measurement - Quantitative Information about Fair Value Measurements for Financial Instruments Measured at Fair Value on Nonrecurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Impaired loans
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value	$ 1,424	$ 1,055
Real estate owned | Residential Real Estate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value	824	$ 417
Real estate owned | Commercial Real Estate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value	$ 155