Derivative Instruments and Hedging Activity (Details - Not designated as hedges) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 28, 2019	Jun. 29, 2018	Jun. 28, 2019	Jun. 29, 2018	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Foreign Currency Derivatives Recorded in Earnings, Net	$ 0	$ 1,600	$ 0	$ 1,100
Euro Member Countries, Euro | Not Designated as Hedging Instrument [Member] | Prepaid Expenses and Other Current Assets [Member] | Foreign Currency Forward Contract
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Notional Amount	2,421		2,421		$ 8,767
Derivative Asset, Fair Value, Gross Asset	27		27		244
Euro Member Countries, Euro | Not Designated as Hedging Instrument [Member] | Other Current Liabilities | Foreign Currency Forward Contract
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Liability, Notional Amount	3,836		3,836		8,771
Derivative Liability, Fair Value, Gross Liability	$ 52		$ 52		$ 249