Changes in Accumulated Other Comprehensive Income (Loss), net - Components of Accumulated Other Comprehensive Income (Loss) Net of Deferred Income Taxes (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Change in net unrealized holding gain on available-for-sale securities, deferred income tax expense (benefits)	$ 62	$ (100)	$ 443	$ (408)
Net Unrealized Gain on Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Change in net unrealized holding gain on available-for-sale securities, deferred income tax expense (benefits)	$ 62	$ (100)	$ 443	$ (408)