Fair Value Measurement - Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available for sale	$ 359,473	$ 346,294
Equity securities	1,039	1,070
(Level 2) [Member] \| Assets Measured at Fair Value on a Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available for sale	359,473	346,294
Equity securities	1,039	1,070
(Level 2) [Member] \| Assets Measured at Fair Value on a Recurring Basis [Member] \| Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Swap asset	8,598	2,837
Swap liability	8,598	2,837
(Level 2) [Member] \| Assets Measured at Fair Value on a Recurring Basis [Member] \| U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available for sale	21,978	30,685
(Level 2) [Member] \| Assets Measured at Fair Value on a Recurring Basis [Member] \| Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available for sale	191,735	172,071
(Level 2) [Member] \| Assets Measured at Fair Value on a Recurring Basis [Member] \| Mortgage-backed Securities in Government Sponsored Entities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available for sale	145,760	143,538
(Level 3) [Member] \| Assets Measured at Fair Value on a Nonrecurring Basis [Member] \| Impaired Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	$ 29	$ 1,803

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Fair value of liability associated with financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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