Revenue - Changes in Deferred Revenue (Detail) $ in Thousands	9 Months Ended
Sep. 30, 2018 USD ($)
Deferred Revenue Disclosure [Abstract]
Deferred Revenue, Beginning Balance	$ 145,344
Deferral of revenue	145,573
Recognition of deferred revenue	(144,935)
Foreign currency translation	(3,525)
Deferred Revenue, Ending Balance	$ 142,457

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