Disclosures about Fair Value of Financial Instruments - Summary of Financial Assets and Financial Liabilities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value Estimate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential mortgage loan commitments	$ 79
Fair Value Estimate | Collateral Appraisal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other real estate owned	78	$ 621
Fair Value Estimate | Discounted cash flow
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest-only GNMA securities	16,272
Fair Value Estimate | Adjusted market bid
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential mortgage loan commitments		$ 69
Impaired loans | Collateral Appraisal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range		8.00%
Impaired loans | Business Asset Valuation
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range		26.00%
Interest-only GNMA securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest-only GNMA securities	$ 16,272
Interest-only GNMA securities | Discounted cash flow
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range	12.00%
Other real estate owned | Collateral Appraisal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range	9.00%	8.00%
Mortgages | Adjusted market bid
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential mortgage loan commitments pull through rate	85.00%	90.00%
Minimum | Impaired loans | Collateral Appraisal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range		8.00%
Minimum | Impaired loans | Business Asset Valuation
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range		8.00%
Minimum | Interest-only GNMA securities | Discounted cash flow
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range	9.00%
Minimum | Other real estate owned | Collateral Appraisal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range	8.00%	8.00%
Minimum | Mortgages | Adjusted market bid
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential mortgage loan commitments pull through rate	85.00%	90.00%
Maximum | Impaired loans | Collateral Appraisal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range		8.00%
Maximum | Impaired loans | Business Asset Valuation
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range		50.00%
Maximum | Interest-only GNMA securities | Discounted cash flow
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range	14.00%
Maximum | Other real estate owned | Collateral Appraisal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range	9.00%	8.00%
Maximum | Mortgages | Adjusted market bid
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential mortgage loan commitments pull through rate	85.00%	90.00%
Real estate | Fair Value Estimate | Collateral Appraisal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	$ 12,767	$ 10,260
Real estate | Impaired loans | Collateral Appraisal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range	8.00%
Real estate | Impaired loans | Business Asset Valuation
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range	37.00%
Real estate | Minimum | Impaired loans | Collateral Appraisal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range	8.00%
Real estate | Minimum | Impaired loans | Business Asset Valuation
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range	34.00%
Real estate | Maximum | Impaired loans | Collateral Appraisal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range	10.00%
Real estate | Maximum | Impaired loans | Business Asset Valuation
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range	45.00%
Commercial and industrial | Fair Value Estimate | Business Asset Valuation
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	$ 1,505	$ 616
Commercial and industrial | Impaired loans | Collateral Appraisal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range	22.00%
Commercial and industrial | Impaired loans | Business Asset Valuation
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range	8.00%
Commercial and industrial | Minimum | Impaired loans | Collateral Appraisal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range	8.00%
Commercial and industrial | Minimum | Impaired loans | Business Asset Valuation
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range	8.00%
Commercial and industrial | Maximum | Impaired loans | Collateral Appraisal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range	50.00%
Commercial and industrial | Maximum | Impaired loans | Business Asset Valuation
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement range	8.00%