Hedging - Derivative Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Foreign currency forward contracts \| Cash flow hedging
Derivative [Line Items]
Total assets	$ 14,616	$ 13
Total liabilities	(571)	(14,508)
Designated as hedging instruments \| Foreign currency forward contracts \| Cash flow hedging
Derivative [Line Items]
Total assets	14,616	13
Total liabilities	(571)	(14,508)
Prepaid expenses and other current assets \| Designated as hedging instruments
Derivative [Line Items]
Fair Value - assets	13,903	13
Other liabilities, current portion \| Designated as hedging instruments
Derivative [Line Items]
Fair Value - liabilities	(505)	(13,642)
Other assets \| Designated as hedging instruments
Derivative [Line Items]
Fair Value - assets	713	0
Other liabilities, excluding current portion \| Designated as hedging instruments
Derivative [Line Items]
Fair Value - liabilities	$ (66)	$ (866)

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Fair value as of the balance sheet date of all foreign currency derivative assets designated as cash flow hedging instruments.

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Fair value as of the balance sheet date of all foreign currency derivative liabilities designated as cash flow hedging instruments.

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