Hedging - Offsetting Derivatives (Details) - Cash flow hedging - Foreign currency forward contracts - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Offsetting Derivative Assets [Abstract]
Gross Amounts Recognized	$ 12,469	$ 13
Offsetting Derivative Liabilities [Abstract]
Gross Amounts Recognized	(2,247)	(15,192)
Designated as hedging instrument
Offsetting Derivative Assets [Abstract]
Gross Amounts Recognized	12,263	13
Gross Amounts Offset	0	0
Gross Amounts Presented	12,263	13
Gross Amounts Not Offset	(2,247)	(13)
Legal Offset	10,016	0
Offsetting Derivative Liabilities [Abstract]
Gross Amounts Recognized	(2,247)	(14,508)
Gross Amounts Offset	0	0
Gross Amounts Presented	(2,247)	(14,508)
Gross Amounts Not Offset	2,247	13
Legal Offset	$ 0	$ (14,495)

Fair value of liability associated with financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

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