Disclosures About Fair Value of Financial Instruments - Summary of Financial Assets and Financial Liabilities Measured at Fair Value on Recurring and Nonrecurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other real estate owned	$ 1,076	$ 816
Impaired loans, net of specific reserves | Collateral Appraisal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weighted average range	8.00%	8.00%
Impaired loans, net of specific reserves | Business Asset Valuation
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weighted average range	16.00%	26.00%
Other real estate owned | Collateral Appraisal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weighted average range	8.00%	8.00%
Residential mortgage loan commitments | Adjusted Market Bid
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential mortgage loan commitments pull through rate	83.00%	90.00%
Fair Value Estimate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential mortgage loan commitments	$ 145	$ 69
Fair Value Estimate | Collateral Appraisal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	5,015	10,260
Other real estate owned	880	621
Fair Value Estimate | Business Asset Valuation
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	$ 6,562	$ 616
Minimum | Impaired loans, net of specific reserves | Collateral Appraisal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weighted average range	8.00%	8.00%
Minimum | Impaired loans, net of specific reserves | Business Asset Valuation
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weighted average range	8.00%	8.00%
Minimum | Other real estate owned | Collateral Appraisal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weighted average range	8.00%	8.00%
Minimum | Residential mortgage loan commitments | Adjusted Market Bid
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential mortgage loan commitments pull through rate	83.00%	90.00%
Maximum | Impaired loans, net of specific reserves | Collateral Appraisal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weighted average range	8.00%	8.00%
Maximum | Impaired loans, net of specific reserves | Business Asset Valuation
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weighted average range	50.00%	50.00%
Maximum | Other real estate owned | Collateral Appraisal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weighted average range	11.00%	8.00%
Maximum | Residential mortgage loan commitments | Adjusted Market Bid
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential mortgage loan commitments pull through rate	83.00%	90.00%