Revenue and Related Contract Costs and Contract Liabilities - Summary of Changes in Contract Costs (Details) $ in Thousands	9 Months Ended
Sep. 30, 2018 USD ($)
Revenue From Contract With Customer [Abstract]
Balance at January 1, 2018	$ 16,878
Additions	53,580
Expenses	(40,641)
Cancelled	(109)
Foreign exchange translation adjustment	(539)
Balance at September 30, 2018	$ 29,169

Amount, after accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=68051541&loc=SL49131252-203054

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant