Revenue from Contracts with Customers (Details 3) $ in Thousands	9 Months Ended
Sep. 30, 2018 USD ($)
Movement in Deferred Revenue [Roll Forward]
Opening balance at January 1, 2018	$ 168,757
Deferral of revenue	127,467
Recognition of unearned revenue	(120,712)
Other	(970)
Balance at September 30, 2018	$ 174,542

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