Derivative Instruments and Hedging Activity (Details - Designated as hedges) - Designated as hedging instrument - USD ($) $ in Thousands	Jun. 26, 2020	Dec. 31, 2019
Derivative [Line Items]
Notional amount total	$ 28,364	$ 34,205
Fair value total	1,317	657
Prepaid expenses
Derivative [Line Items]
Notional amount, asset	7,319	7,558
Fair value, asset	159	188
Prepaid expenses | Foreign currency forward contract | Yen
Derivative [Line Items]
Notional amount, asset	0	1,025
Fair value, asset	0	10
Prepaid expenses | Foreign currency forward contract | Euro
Derivative [Line Items]
Notional amount, asset	5,084	3,466
Fair value, asset	22	83
Prepaid expenses | Precious metal swaps
Derivative [Line Items]
Notional amount, asset	0	1,116
Fair value, asset	0	34
Prepaid expenses | Copper swaps
Derivative [Line Items]
Notional amount, asset	2,235	1,951
Fair value, asset	137	61
Other assets | Precious metal swaps
Derivative [Line Items]
Notional amount, asset	0	157
Fair value, asset	0	1
Other liabilities and accrued items
Derivative [Line Items]
Notional amount, liability	20,208	26,341
Fair value, liability	1,452	841
Other liabilities and accrued items | Foreign currency forward contract | Yen
Derivative [Line Items]
Notional amount, liability	2,031	2,355
Fair value, liability	25	12
Other liabilities and accrued items | Foreign currency forward contract | Euro
Derivative [Line Items]
Notional amount, liability	11,974	15,686
Fair value, liability	420	183
Other liabilities and accrued items | Precious metal swaps
Derivative [Line Items]
Notional amount, liability	5,910	7,034
Fair value, liability	1,004	618
Other liabilities and accrued items | Copper swaps
Derivative [Line Items]
Notional amount, liability	293	1,266
Fair value, liability	3	28
Other long-term liabilities
Derivative [Line Items]
Notional amount, liability	837	149
Fair value, liability	24	5
Other long-term liabilities | Foreign currency forward contract | Yen
Derivative [Line Items]
Notional amount, liability	112	0
Fair value, liability	1	0
Other long-term liabilities | Foreign currency forward contract | Euro
Derivative [Line Items]
Notional amount, liability	553	0
Fair value, liability	14	0
Other long-term liabilities | Precious metal swaps
Derivative [Line Items]
Notional amount, liability	172	149
Fair value, liability	$ 9	$ 5