Revenue Recognition - Deferred Revenue Activity (Details) $ in Thousands	6 Months Ended
Jun. 30, 2019 USD ($)
Movement in Deferred Revenue [Roll Forward]
Balance as of December 31, 2018	$ 9,845
Increases to deferred revenue and customer deposits	29,883
Recognition of revenue	(21,308)
Foreign exchange rate changes	(88)
Balance as of June 30, 2019	$ 18,332

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