Income Taxes - Schedule of Components of Investments in Qualified Affordable Housing Projects (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Tax credits and other tax benefits - decrease in tax expense	$ (1,993)	$ (1,753)	$ (954)
Amortization - increase in tax expense	$ 1,814	$ 1,611	$ 757