Investment Securities - Summary of Equity Securities (Detail) - Marketable Equity Securities [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Debt Securities, Available-for-sale [Line Items]
Net gains recognized during the period	$ 43	$ 55	$ 65	$ 244
Net gains recognized during the period on equity securities sold	1	2	7	134
Unrealized gains recognized during the period on equity securities still held at period end	43	64	114	122
Unrealized losses recognized during the period on equity securities still held at period end	$ (1)	$ (11)	$ (56)	$ (12)