Fair Value of Financial Instruments (Foreign Currency Forward Contracts) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Derivative [Line Items]
Foreign Currency Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months	$ 500		$ 500
Foreign Currency Transaction Gain (Loss), before Tax	(600)	$ 300	(700)	$ 300
Derivative Assets and Liabilities at Fair Value [Abstract]
Derivative Assets (Liabilities), at Fair Value, Net	1,400		1,400		$ (5,700)
Prepaid Expenses And Other Current Assets and Non-current Other Assets [Domain]
Derivative Assets and Liabilities at Fair Value [Abstract]
Fair value, assets	3,039		3,039
Derivative Liability, Fair Value, Gross Liability	(1,607)		(1,607)
Derivative Assets (Liabilities), at Fair Value, Net	1,432		1,432
Other Current Liabilities [Member]
Derivative Assets and Liabilities at Fair Value [Abstract]
Fair value, assets					350
Derivative Liability, Fair Value, Gross Liability					(6,023)
Derivative Assets (Liabilities), at Fair Value, Net					(5,673)
Foreign Currency Forward Contracts [Member]
Derivative [Line Items]
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments	400	(400)	300	(600)
Designated as Hedging Instrument [Member] | Foreign Currency Forward Contracts [Member] | Prepaid Expenses And Other Current Assets and Non-current Other Assets [Domain]
Derivative Assets and Liabilities at Fair Value [Abstract]
Fair value, assets	3,025		3,025
Derivative Liability, Fair Value, Gross Liability	(1,487)		(1,487)
Derivative Assets (Liabilities), at Fair Value, Net	1,538		1,538
Designated as Hedging Instrument [Member] | Foreign Currency Forward Contracts [Member] | Other Current Liabilities [Member]
Derivative Assets and Liabilities at Fair Value [Abstract]
Fair value, assets					346
Derivative Liability, Fair Value, Gross Liability					(5,945)
Derivative Assets (Liabilities), at Fair Value, Net					(5,599)
Not Designated as Hedging Instrument [Member] | Foreign Currency Forward Contracts [Member]
Derivative [Line Items]
Notional amount of cash flow hedges	34,300		34,300
Not Designated as Hedging Instrument [Member] | Foreign Currency Forward Contracts [Member] | Prepaid Expenses And Other Current Assets and Non-current Other Assets [Domain]
Derivative Assets and Liabilities at Fair Value [Abstract]
Fair value, assets	14		14
Derivative Liability, Fair Value, Gross Liability	(120)		(120)
Derivative Assets (Liabilities), at Fair Value, Net	(106)		(106)
Not Designated as Hedging Instrument [Member] | Foreign Currency Forward Contracts [Member] | Other Current Liabilities [Member]
Derivative Assets and Liabilities at Fair Value [Abstract]
Fair value, assets					4
Derivative Liability, Fair Value, Gross Liability					(78)
Derivative Assets (Liabilities), at Fair Value, Net					$ (74)
Cash Flow Hedging [Member] | Foreign Currency Forward Contracts [Member]
Derivative [Line Items]
Notional amount of cash flow hedges	136,900		136,900
Cash flow hedges realized gains (losses)	$ (400)	$ 200	$ (1,600)	$ 600