Derivative Financial Instruments Derivatives Not Designated as Hedging Relationships (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Income (Expense) [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments	$ (6,281)	$ 537	$ (3,145)
Interest Rate Cap [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	$ (274)	$ 129	$ 0

Amount of gain (loss) recognized in earnings in the period from the increase (decrease) in fair value of foreign currency derivatives not designated 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

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5618551-113959

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