Income Taxes - Income Before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Domestic	$ 20,061	$ 22,303	$ 11,347
Foreign	7,310	8,406	7,973
Income before income taxes	$ 27,371	$ 30,709	$ 19,320