Summary of Significant Accounting Policies - Schedule of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 39,770	$ 36,512	$ 37,325
Current period other comprehensive income	1,871	(3,866)	(1,099)
Ending balance	41,512	39,770	$ 36,512
Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(5,028)
Current period other comprehensive income	(1,871)
Ending balance	$ (3,157)	$ (5,028)