Changes in Accumulated Other Comprehensive Income (Loss), net - Components of Accumulated Other Comprehensive Income (Loss) Net of Deferred Taxes (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Change in net unrealized holding gain on available-for-sale securities, deferred tax expense (benefits)	$ 167	$ (57)	$ 382	$ (308)
Net Unrealized Gain on Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Change in net unrealized holding gain on available-for-sale securities, deferred tax expense (benefits)	$ 167	$ (57)	$ 382	$ (308)