Fair Value Measurement - Quantitative Information about Recurring Level 3 Fair Value Measurements (Detail) - Mortgage servicing rights $ in Thousands	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Mortgages servicing rights, fair value	$ 5,603	$ 5,092
Minimum | Valuation Technique, Discounted Cash Flow | Measurement Input, Constant Prepayment Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.12	0.14
Minimum | Valuation Technique, Discounted Cash Flow | Measurement Input, Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.10	0.10
Maximum | Valuation Technique, Discounted Cash Flow | Measurement Input, Constant Prepayment Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.17	0.200
Maximum | Valuation Technique, Discounted Cash Flow | Measurement Input, Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.14	0.14
Weighted Average | Valuation Technique, Discounted Cash Flow | Measurement Input, Constant Prepayment Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.142	0.176
Weighted Average | Valuation Technique, Discounted Cash Flow | Measurement Input, Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.12	0.12