Accumulated Other Comprehensive Income - Schedule of Reclassifications Out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Realized gains on sales of investment securities	$ 3,152	$ (7,656)	$ 2,343
Amount reclassified from accumulated other comprehensive income	776	(1,883)	(899)
Amount reclassified from accumulated other comprehensive income	$ 2,376	$ (5,773)	1,444
Income Tax Expense [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amount reclassified from accumulated other comprehensive income			$ 899