Summary of Significant Accounting Policies - Other (Income) Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Foreign currency (gains) losses	$ (253)	$ 853	$ 1,752
Tax indemnification income	(8,367)	(1,055)	(1,655)
Other income	(18)	(18)	(32)
Total other (income) expense	$ (8,638)	$ (220)	$ 65