Derivative Instruments - Derivatives Not Designated as Hedging Instruments (Details) - Other expense - net - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments
Amount of Gain or (Loss) Recognized in Earnings on Derivatives Not Designated as Hedging Instruments	$ 294	$ (240)	$ (8,981)	$ 1,050
Foreign exchange contracts
Derivative Instruments
Amount of Gain or (Loss) Recognized in Earnings on Derivatives Not Designated as Hedging Instruments	$ 294	$ (240)	$ (8,981)	$ 1,050

Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

Name:	us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration