Commitments and Contingencies - Summary of Open Loan Commitments (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Commitments to Extend Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Contractual notional amount of instruments	$ 50,158	$ 54,458
Unused Commercial Lines of Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Contractual notional amount of instruments	45,912	62,910
Unused Home Equity Lines of Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Contractual notional amount of instruments	31,733	32,701
Unused Lines of Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Contractual notional amount of instruments	12,109	17,048
Standby Letters of Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Contractual notional amount of instruments	$ 1,046	$ 143