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	Jun. 30, 2019	Dec. 31, 2018
Assets:
Impaired loans	$ 17,385	$ 19,702
Loans held for sale	1,391	1,113
Other real estate owned and other repossessed assets	532	830
(Level 1)
Assets:
Impaired loans	0	0
Loans held for sale	0	0
Other real estate owned and other repossessed assets	0	0
(Level 2)
Assets:
Impaired loans	0	0
Loans held for sale	1,391	1,113
Other real estate owned and other repossessed assets	0	0
(Level 3)
Assets:
Impaired loans	17,385	19,702
Loans held for sale	0	0
Other real estate owned and other repossessed assets	$ 532	$ 830