Loans - Summary of Activity in Allowance for Loan and Lease Losses (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Loans and Leases Receivable Disclosure [Line Items]
Beginning balance	$ 2,114	$ 3,187	$ 2,000	$ 3,262
Provision (credit) for loan losses	500		500
Loans charged-off	(62)	(181)	(67)	(483)
Recoveries	98	12	217	239
Ending balance	2,650	3,018	2,650	3,018
Commercial [Member]
Loans and Leases Receivable Disclosure [Line Items]
Beginning balance	1,243	1,445	1,235	1,448
Provision (credit) for loan losses	360		360
Loans charged-off		0		(214)
Recoveries	2	6	10	217
Ending balance	1,605	1,451	1,605	1,451
Residential [Member]
Loans and Leases Receivable Disclosure [Line Items]
Beginning balance	573	1,172	573	1,250
Provision (credit) for loan losses	100		100
Loans charged-off	(60)		(60)	(83)
Recoveries	88		88	5
Ending balance	701	1,172	701	1,172
Consumer [Member]
Loans and Leases Receivable Disclosure [Line Items]
Beginning balance	298	570	192	564
Provision (credit) for loan losses	40		40
Loans charged-off	(2)	(181)	(7)	(186)
Recoveries	8	6	119	17
Ending balance	$ 344	$ 395	$ 344	$ 395