Fair Value Measurements (Derivative Financial Instruments) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Derivative [Line Items]
Cash held as collateral	$ 1,451		$ 1,451		$ 3,962
Foreign Currency Derivatives Contracts [Member]
Derivative [Line Items]
Notional amount of foreign currency derivative contracts	12,506		12,506		44,438
Fair value of foreign currency derivatives contracts	856		856		42
Foreign Currency Derivatives Contracts [Member] | Other (Income) Expense [Member]
Derivative [Line Items]
Gain (losses) on Derivative Instruments Recognized in Statements of Operations	(19)	$ 44	194	$ 132
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	5		5		66
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	$ 861		$ 861		$ 108