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Financial Instruments - Narrative (Details) - USD ($) $ in Thousands | 6 Months Ended |
--- | --- | ---
Jun. 29, 2019 | Dec. 29, 2018
Derivative [Line Items] |  |
Restricted cash in other current assets as collateral related to open derivative contracts | $ 1,800 | $ 3,600
Commodity Contracts [Member] |  |
Derivative [Line Items] |  |
Deferred net losses, net of tax, included in AOCI | (42) |
Cash Flow Hedging [Member] | Commodity Contracts [Member] | Long [Member] |  |
Derivative [Line Items] |  |
Open option contracts written, at fair value | $ 55,600 |
Time period for open copper future contract purchases | 13 months |
Fair value of future contracts with net loss position | $ 17 |
Fair Value Hedging [Member] | Commodity Contracts [Member] | Short [Member] |  |
Derivative [Line Items] |  |
Fair value of future contracts with net loss position | 32 |
Open future contracts to sell copper | $ 1,200 |
Time period for open copper future contract sales | 9 months |

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