Financial Instruments - Offsetting of Foreign Currency Derivative Contracts (Details) - Foreign currency exchange contract [Member] - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Offsetting Liabilities [Line Items]
Gross Assets Recognized	$ 430	$ 2,138
Gross Amounts Offset in the Condensed Consolidated Balance Sheets	0	0
Net Amounts Presented in Condensed Consolidated Balance Sheets	430	2,138
Gross Amounts Not Offset in Condensed Consolidated Balance Sheets, Financial Instruments	430	0
Gross Amounts Not Offset in Condensed Consolidated Balance Sheets, Cash Collateral Pledged	0	0
Net Amount	0	2,138
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	833	0
Gross Amounts Offset in the Condensed Consolidated Balance Sheets	0	0
Net Amounts Presented in Condensed Consolidated Balance Sheets	833	0
Gross Amounts Not Offset in Condensed Consolidated Balance Sheets, Financial Instruments	430	0
Gross Amounts Not Offset in Condensed Consolidated Balance Sheets, Cash Collateral Received	0	0
Net Amount	$ 403	$ 0

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