Derivatives and Hedging Activities Derivative Instruments and Hedging Activities - Cash Flow Hedge Activity Included in Accumulated Other Comprehensive Income (Loss) (Details) - Cash Flow Hedging [Member] - Cost of Sales [Member] - Foreign Exchange Forward [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative Instruments, Gain Recognized in Other Comprehensive Income (Loss), Effective Portion	$ 296
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion	$ 885