Commitments, Contingencies and Off-Balance-Sheet Risk - Contractual Amounts of Financial Instruments with Off-Balance-Sheet Risk (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fixed Rate	$ 10,897	$ 15,784
Variable Rate	473,681	434,578
Lines of Credit and Construction Loans [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fixed Rate	10,291	15,155
Variable Rate	431,564	396,516
Overdraft Protection [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fixed Rate	6	5
Variable Rate	41,231	37,286
Letters of Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fixed Rate	600	624
Variable Rate	$ 886	$ 776