Loans - Summary of Activity in Allowance for Loan and Lease Losses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Loans and Leases Receivable Disclosure [Line Items]
Beginning balance	$ 3,093	$ 3,008
Provision for loan losses	0	0
Loans charged off	(124)	(37)
Recoveries of loans previously charged off	293	122
Total ending allowance balance	3,262	3,093
Commercial [Member]
Loans and Leases Receivable Disclosure [Line Items]
Beginning balance	1,369	1,345
Provision for loan losses	0	0
Loans charged off	(1)
Recoveries of loans previously charged off	80	24
Total ending allowance balance	1,448	1,369
Residential [Member]
Loans and Leases Receivable Disclosure [Line Items]
Beginning balance	1,246	1,224
Provision for loan losses	0	0
Recoveries of loans previously charged off	4	22
Total ending allowance balance	1,250	1,246
Consumer [Member]
Loans and Leases Receivable Disclosure [Line Items]
Beginning balance	478	439
Provision for loan losses	0	0
Loans charged off	(123)	(37)
Recoveries of loans previously charged off	209	76
Total ending allowance balance	$ 564	$ 478