Provision for Income Taxes - Provision for Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Expected tax expense, at the U.S. federal statutory income tax rate of 35% in 2017 and 21% in 2018	$ 1,038	$ 1,701
Domestic production activities deduction		(145)
State income taxes	172	132
Other, net	9	20
Total income tax expense	$ 1,219	$ 1,708