Loans - Summary of Activity in Allowance for Loan and Lease Losses (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Loans and Leases Receivable Disclosure [Line Items]
Beginning balance	$ 2,703	$ 2,000
Provision for loan losses	0	0
Loans charged-off	(16)	(5)
Recoveries	12	13
Ending balance	2,699	2,008
Commercial [Member]
Loans and Leases Receivable Disclosure [Line Items]
Beginning balance	1,609	1,235
Provision for loan losses	0	0
Loans charged-off		0
Recoveries	5	6
Ending balance	1,614	1,241
Residential [Member]
Loans and Leases Receivable Disclosure [Line Items]
Beginning balance	745	573
Provision for loan losses	0	0
Loans charged-off	0	0
Recoveries	0	0
Ending balance	745	573
Consumer [Member]
Loans and Leases Receivable Disclosure [Line Items]
Beginning balance	349	192
Provision for loan losses	0	0
Loans charged-off	(16)	(5)
Recoveries	7	7
Ending balance	$ 340	$ 194