Loans - Composition of Nonaccrual Loans and Impaired Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Disclosure [Abstract]
Loans on nonaccrual	$ 2,014	$ 1,313	$ 1,684
Loans 90 days past due and still accruing	0	0	0
Impaired loans on nonaccrual included above		296	254
Total recorded investment in impaired loans	3,252	3,051	7,114
Average recorded investment of impaired loans	3,161	5,491	5,608
Accruing troubled debt restructures	2,361	2,559	2,749
Interest income not recorded on nonaccrual loans according to their original terms	67	64	51
Interest income on nonaccrual loans actually recorded	0	0	0
Interest income recognized on impaired loans	$ 103	$ 196	$ 182