Goodwill (Details) $ in Thousands	3 Months Ended
Mar. 31, 2018 USD ($)
Goodwill [Roll Forward]
Net goodwill as of December 31, 2016	$ 199,946
Foreign exchange impact	796
Net goodwill as of September 30, 2017	200,743
North America
Goodwill [Roll Forward]
Net goodwill as of December 31, 2016	170,685
Foreign exchange impact	(32)
Net goodwill as of September 30, 2017	170,653
International
Goodwill [Roll Forward]
Net goodwill as of December 31, 2016	29,262
Foreign exchange impact	828
Net goodwill as of September 30, 2017	$ 30,090

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

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