Derivative Financial Instruments Derivative Instruments and Hedging Activities - Cash Flow Hedge Activity Included in Accumulated Other Comprehensive Income (Loss) (Details) - Cost of Sales [Member] - Foreign Exchange Forward [Member] - Cash Flow Hedging [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative Instruments, Gain Recognized in Other Comprehensive Income (Loss), Effective Portion	$ 2,622	$ 0
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion	$ 235	$ 0