Fair Value Measurements - Financial Assets and Financial Liabilities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Items Measured on a Recurring Basis | U.S. Agency Obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	$ 100,015	$ 81,581
Items Measured on a Recurring Basis | Equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	9,519	8,700
Items Measured on a Recurring Basis | Interest rate swap asset
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	557
Items Measured on a Recurring Basis | Interest rate swap liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	636
Items Measured on a Recurring Basis | Level 1 Inputs | Equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	9,519	8,700
Items Measured on a Recurring Basis | Level 2 Inputs | U.S. Agency Obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	100,015	81,581
Items Measured on a Recurring Basis | Level 2 Inputs | Interest rate swap asset
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	557
Items Measured on a Recurring Basis | Level 2 Inputs | Interest rate swap liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	636
Items Measured on a Non-Recurring Basis | Other real estate owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	6,231	8,186
Items Measured on a Non-Recurring Basis | Loans measured for impairment based on the fair value of the underlying collateral
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	13,001	16,496
Items Measured on a Non-Recurring Basis | Level 3 Inputs | Other real estate owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	6,231	8,186
Items Measured on a Non-Recurring Basis | Level 3 Inputs | Loans measured for impairment based on the fair value of the underlying collateral
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	$ 13,001	$ 16,496