Loans - Summary of Activities in Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for Loan Losses
Balance at beginning of year				$ 7,228				$ 6,775	$ 7,228	$ 6,775	$ 6,868
Provision for loan losses	$ 1,995	$ 1,987	$ 1,569	$ 1,430	$ 728	$ 247	$ 133	$ 30	6,981	1,138	324
Loans charged off									(720)	(841)	(580)
Recoveries									183	156	163
Balance at ending of year	13,672				7,228				13,672	7,228	6,775
Allowance for Unfunded Loan Commitments & Letters of Credit	641				479				641	479	274
Total Allowance for Credit Losses	$ 14,313				$ 7,707				$ 14,313	$ 7,707	$ 7,049