Income Taxes - Schedule of Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current income tax (benefit) expense:
Domestic	$ (41)	$ 42	$ 147
Foreign	3,062	1,856	1,614
Total income tax expense	3,021	1,898	1,761
Deferred income tax (benefit) expense:
Domestic	(233)	147	(360)
Foreign	(107)	(8,875)	102
Total income tax expense	(340)	(8,728)	(258)
Income tax expense (benefit)	$ 2,681	$ (6,830)	$ 1,503