Reconciliation of Total Amounts of Unrecognized Tax Benefits Excluding Interest and Penalties (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Beginning Balance	$ 17,403	$ 17,133	$ 16,515
Gross increases - tax positions in prior periods	92	13	40
Gross decreases - tax positions in prior periods	(12)
Gross increases - current period tax positions	265	923	2,112
Settlements	(177)	(924)	(871)
Foreign currency translation adjustments	695	258	(663)
Ending Balance	$ 18,266	$ 17,403	$ 17,133