Changes in Unearned Revenue (Detail) $ in Thousands	9 Months Ended
Sep. 30, 2018 USD ($)
Revenue Recognition And Deferred Revenue [Abstract]
Beginning balance	$ 4,889
Additions to unearned revenue	15,467
Reclassified to revenue	(14,193)
Currency impacts	(35)
Ending balance	$ 6,128

Amount of deferred revenue recognized for transactions arising during the current reporting period. Deferred revenue is a liability as of the balance sheet date related to a revenue producing activity for which revenue has not yet been recognized. Generally, an Entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

No definition available.

Name:	us-gaap_DeferredRevenueAdditions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration