Provision for Income Taxes - Provision for Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Expected tax expense, at the U.S. federal statutory income tax rate of 21%	$ 1,182	$ 1,077
State income taxes	197	179
FDII benefit	(28)	(119)	$ (98)
Other, net	5	4
Total income tax expense	$ 1,356	$ 1,141