Fair Value Measurement and Fair Value of Financial Instruments - Fair Value of Financial Assets Measured on Non-recurring Basis (Detail) - Fair Value, Measurements, Non-recurring - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Individually evaluated loans	$ 2,417
Loans held for sale	1,335	$ 1,743
Impaired loans		5,789
Other real estate owned and other repossessed assets		563
Quoted Prices in Active  Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Individually evaluated loans	0
Loans held for sale	0	0
Impaired loans		0
Other real estate owned and other repossessed assets		0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Individually evaluated loans	0
Loans held for sale	1,335	1,743
Impaired loans		0
Other real estate owned and other repossessed assets		0
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Individually evaluated loans	2,417
Loans held for sale	$ 0	0
Impaired loans		5,789
Other real estate owned and other repossessed assets		$ 563