Allowance for Loan Losses - Summary of Roll Forward of Accruing and Nonaccrual TDRs (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2020 USD ($)
Financing Receivable, Impaired [Line Items]
Beginning Balance	$ 7,562	[1]
Ending Balance	12,899
Accruing
Financing Receivable, Impaired [Line Items]
Beginning Balance	3,270
Charge-offs	(183)
Payments and other adjustments	(615)
Release TDR designation	(50)
Transfer	0
Ending Balance	2,422
Nonaccrual
Financing Receivable, Impaired [Line Items]
Beginning Balance	1,352
Charge-offs	(327)
Payments and other adjustments	(36)
New TDR designation	611
Release TDR designation	0
Transfer	0
Ending Balance	1,600
Troubled Debt Restructuring
Financing Receivable, Impaired [Line Items]
Beginning Balance	4,622
Charge-offs	(510)
Payments and other adjustments	(651)
New TDR designation	611
Release TDR designation	(50)
Transfer	0
Ending Balance	$ 4,022

[1] Derived from audited December 31, 2019 Consolidated Financial Statements.