Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
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Fair value of the assets less the liabilities of a derivative or group of derivatives.

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The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Fair value of financial and nonfinancial obligations.

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Amount of cash and cash equivalents restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair Value Measurements (Derivative Financial Instruments) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Derivative [Line Items]
Cash held as collateral	$ 216		$ 1,451
Foreign Currency Derivatives Contracts [Member]
Derivative [Line Items]
Notional amount of foreign currency derivative contracts	0		2,866
Fair value of foreign currency derivatives contracts	0		63
Foreign Currency Derivatives Contracts [Member] \| Other (Income) Expense [Member]
Derivative [Line Items]
Gain (losses) on Derivative Instruments Recognized in Statements of Operations	(50)	$ 175
Foreign Currency Derivatives Contracts [Member] \| Derivative Financial Instruments, Liabilities [Member] \| Not Designated as Hedging Instrument [Member] \| Accrued Expenses And Other Liabilities [Member]
Derivative [Line Items]
Liabilities	0		2
Foreign Currency Derivatives Contracts [Member] \| Derivative Financial Instruments, Assets [Member] \| Not Designated as Hedging Instrument [Member] \| Prepaid Expenses and Other Current Assets [Member]
Derivative [Line Items]
Assets	$ 0		$ 65