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, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans and leases	$ 19,702	$ 22,591
Loans held for sale	1,113	456
Other real estate owned and other repossessed assets	830	843
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	1,113	456
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans and leases	19,702	22,591
Other real estate owned and other repossessed assets	$ 830	$ 843