Derivative Instruments And Hedging Activities - Derivative Instruments Not Designated As Hedging Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Liability derivative instruments not designated as hedging instruments	$ 3,156	$ 3,984
Accrued Liabilities | Foreign Exchange Contracts
Derivative [Line Items]
Liability derivative instruments not designated as hedging instruments	3,156	3,454
Other Non-Current Liabilities | Foreign Exchange Contracts
Derivative [Line Items]
Liability derivative instruments not designated as hedging instruments	$ 0	$ 530