Estimated Fair Value of Financial Instruments and Fair Value Measurement - Fair Value of Assets Measured on Non-recurring Basis (Detail) - Fair Value, Measurements, Non-recurring - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Assets:
Impaired loans	$ 17,653	$ 19,702
Loans held for sale	3,077	1,113
Properties held for sale	1,836
Other real estate owned and other repossessed assets	944	830
(Level 1)
Assets:
Impaired loans	0	0
Loans held for sale	0	0
Properties held for sale	0
Other real estate owned and other repossessed assets	0	0
(Level 2)
Assets:
Impaired loans	0	0
Loans held for sale	3,077	1,113
Properties held for sale	0
Other real estate owned and other repossessed assets	0	0
(Level 3)
Assets:
Impaired loans	17,653	19,702
Loans held for sale	0	0
Properties held for sale	1,836
Other real estate owned and other repossessed assets	$ 944	$ 830