Derivative Instruments And Hedging Activities - Impact Of Derivative Instruments Not Designated As Hedging Instruments On Consolidated Statement Of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Earnings on Derivative Instruments	$ 818	$ 1,198	$ (18,014)
Foreign Exchange Contracts [Member] | Other Income (Expense), Net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Earnings on Derivative Instruments	$ 818	$ 1,198	$ (18,014)