Fair Value - Summary of Quantitative Information about Level 3 Fair Value Measurements (Detail) - Fair Value, Nonrecurring [Member] - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Disclosure Of Other Real Estate Owned Measured On Nonrecurring Vasis Valuation Techniques [Line Items]
Impaired loans, net	$ 8,233	$ 2,187
Selling Costs [Member]
Disclosure Of Other Real Estate Owned Measured On Nonrecurring Vasis Valuation Techniques [Line Items]
Impaired loans, net	$ 8,233	$ 2,097
Valuation Technique	Discounted appraised value	Discounted appraised value
Unobservable Input	Selling costs	Selling costs
Weighted Average	7.00%	10.00%
OREO	$ 227
Valuation Technique	Discounted appraised value
Unobservable Input	Selling costs
Weighted Average	7.00%
Discount Rate [Member]
Disclosure Of Other Real Estate Owned Measured On Nonrecurring Vasis Valuation Techniques [Line Items]
Impaired loans, net		$ 90
Valuation Technique		Discounted cash flows
Unobservable Input		Discount rate
Weighted Average		6.00%