Securities - Schedule of Gross Realized Gains and Losses on the Sales and Calls of Securities as well as Gains and Losses on Equity Securities as well as Result of the Adoption of the ASU 2016-01 (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Available-for-Sale Securities, Gross Unrealized Gain (Loss) [Line Items]
Net securities gains (losses)	$ 4,320	$ (900)	$ 567
Debt Securities [Member]
Available-for-Sale Securities, Gross Unrealized Gain (Loss) [Line Items]
Gross realized gains	1,497	128	675
Gross realized losses	(981)	(46)	(108)
Net gains on debt securities	516	82	$ 567
Equity Securities [Member]
Available-for-Sale Securities, Gross Unrealized Gain (Loss) [Line Items]
Unrealized gains (losses) recognized on securities still held	1,226	(986)
Net realized gains recognized on securities sold	2,578	4
Net gains (losses) on equity securities	$ 3,804	$ (982)