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Financial Instruments - Narrative (Details) - USD ($) $ in Thousands | 6 Months Ended |
--- | --- | ---
Jun. 27, 2020 | Dec. 28, 2019
Derivative [Line Items] |  |
Restricted cash in other current assets as collateral related to open derivative contracts | $ 100 | $ 200
Commodity Contracts [Member] |  |
Derivative [Line Items] |  |
Deferred net losses, net of tax, included in AOCI | (300) |
Cash Flow Hedging [Member] | Commodity Contracts [Member] | Long [Member] |  |
Derivative [Line Items] |  |
Open option contracts written, at fair value | $ 25,400 |
Time period for open copper future contract purchases | 15 months |
Fair value of future contracts with net gain (loss) position | $ 1,200 |
Fair Value Hedging [Member] | Commodity Contracts [Member] | Short [Member] |  |
Derivative [Line Items] |  |
Fair value of future contracts with net gain (loss) position | (88) |
Open future contracts to sell copper | $ 600 |
Time period for open copper future contract sales | 9 months |

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