Loans - Schedule of Impaired Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Receivables [Abstract]
Impaired loans without a valuation allowance	$ 5,172	$ 2,420
Impaired loans with a valuation allowance	9,360	641
Total impaired loans	14,532	3,061
Valuation allowance related to impaired loans	1,657	197
Total non-accrual loans	9,404	3,400
Total loans past-due ninety days or more and still accruing	0	0
Average investment in impaired loans	10,234	2,649	$ 1,958
Interest income recognized on impaired loans	269	118	69
Interest income recognized on a cash basis on impaired loans	$ 135	$ 9	$ 17