Hedging - Offsetting Derivatives (Details) - Foreign currency forward contracts - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Offsetting Derivative Assets [Abstract]
Gross Amounts Recognized	$ 13	$ 15,593
Gross Amounts Offset	0	0
Gross Amount Presented	13	15,593
Gross Amount Not Offset	(13)	(144)
Legal Offset	0	15,449
Offsetting Derivative Liabilities [Abstract]
Gross Amounts Recognized	(14,508)	(144)
Gross Amounts Offset	0	0
Gross Amount Presented	(14,508)	(144)
Gross Amount Not Offset	13	144
Legal Offset	$ (14,495)	$ 0

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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