Fair Value Measurement and Fair Value of Financial Instruments - Fair Value of Assets Measured on Non-recurring Basis (Detail) - Fair Value, Measurements, Non-recurring - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets:
Impaired loans	$ 4,224	$ 5,789
Loans held for sale	4,197	1,743
Other real estate owned and other repossessed assets		563
(Level 1)
Assets:
Impaired loans	0	0
Loans held for sale	0	0
Other real estate owned and other repossessed assets		0
(Level 2)
Assets:
Impaired loans	0	0
Loans held for sale	4,197	1,743
Other real estate owned and other repossessed assets		0
(Level 3)
Assets:
Impaired loans	4,224	5,789
Loans held for sale	$ 0	0
Other real estate owned and other repossessed assets		$ 563