Fair Value Measurement - Quantitative Information about Fair Value Measurements for Financial Instruments Measured at Fair Value on Nonrecurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Impaired Originated And PNCI Loans
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value	$ 1,055	$ 281
Foreclosed Assets | Residential Real Estate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value	$ 417	693
Foreclosed Assets | Commercial Real Estate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value		$ 618
Level 3 | Sales Comparison Approach | Minimum | Impaired Originated And PNCI Loans | Adjustment for differences between comparable sales
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financial Instruments, Measurement Input		7400.00%
Level 3 | Sales Comparison Approach | Minimum | Foreclosed Assets | Residential Real Estate | Adjustment for differences between comparable sales
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financial Instruments, Measurement Input		4700.00%
Level 3 | Sales Comparison Approach | Minimum | Foreclosed Assets | Commercial Real Estate | Adjustment for differences between comparable sales
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financial Instruments, Measurement Input		8400.00%
Level 3 | Sales Comparison Approach | Maximum | Impaired Originated And PNCI Loans | Adjustment for differences between comparable sales
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financial Instruments, Measurement Input		2300.00%
Level 3 | Sales Comparison Approach | Maximum | Foreclosed Assets | Residential Real Estate | Adjustment for differences between comparable sales
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financial Instruments, Measurement Input		3900.00%
Level 3 | Sales Comparison Approach | Maximum | Foreclosed Assets | Commercial Real Estate | Adjustment for differences between comparable sales
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financial Instruments, Measurement Input		1900.00%
Level 3 | Sales Comparison Approach | Weighted Average | Impaired Originated And PNCI Loans | Adjustment for differences between comparable sales
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financial Instruments, Measurement Input		1976.00%
Level 3 | Sales Comparison Approach | Weighted Average | Foreclosed Assets | Residential Real Estate | Adjustment for differences between comparable sales
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financial Instruments, Measurement Input		313.00%
Level 3 | Sales Comparison Approach | Weighted Average | Foreclosed Assets | Commercial Real Estate | Adjustment for differences between comparable sales
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financial Instruments, Measurement Input		8400.00%