Fair Value Measurements - Financial Assets and Financial Liabilities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Mar. 31, 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	$ 86,114	$ 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	9,565	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	415
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	(416)
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	9,565	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	86,114	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	415
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	(416)
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	8,265	8,186
Items Measured on a Non-Recurring Basis | Loans Measured for Impairment Based on the Fair Value of Underlying Collateral
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	12,633	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	8,265	8,186
Items Measured on a Non-Recurring Basis | Level 3 Inputs | Loans Measured for Impairment Based on the Fair Value of Underlying Collateral
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	$ 12,633	$ 16,496