Commitments and Contingencies - Additional Information (Detail) $ in Thousands	Dec. 31, 2020 USD ($)
Commitments And Contingencies [Line Items]
Reserve for sold mortgages	$ 309
Letter of Credit [Member]
Commitments And Contingencies [Line Items]
Reserve for off-balance sheet credits	498
Maximum [Member] | Letter of Credit [Member]
Commitments And Contingencies [Line Items]
Off-balance sheet risks, amount, liability	$ 70,600