Provision for Income Taxes - Provision for Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Expected tax expense, at the U.S. federal statutory income tax rate of 21%			$ 2,431	$ 2,430
State income taxes			403	396
FDII benefit			(148)		$ (98)
Other, net			10	20
Total income tax expense	$ 1,555	$ 1,627	$ 2,696	$ 2,846