Derivatives and Hedging Activities Assets Liabilities Balance Sheet Location (Details) - Foreign Exchange Contract [Member] - USD ($) $ in Thousands	Jun. 29, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Derivative Asset, Current	$ 14	$ 33
Derivative Liability, Current	298	4
Not Designated as Hedging Instrument [Member] | Prepaid Expenses and Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Current	14	33
Not Designated as Hedging Instrument [Member] | Accrued Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Current	$ 298	$ 4