Fair Value Measurements - Summary of Assets Measured at Fair Value on Nonrecurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	$ 3,500	$ 3,491
Other real estate owned, net	3,663	4,284
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	3,500	3,491
Other real estate owned, net	3,663	4,284
Fair Value, Measurements, Nonrecurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	3,500	3,491
Other real estate owned, net	$ 3,663	$ 4,284