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Financial Instruments - Narrative (Details) - USD ($)
$ in Thousands
3 Months Ended
Mar. 30, 2019
Dec. 29, 2018
Derivative [Line Items]    
Restricted cash in other current assets as collateral related to open derivative contracts $ 500 $ 3,600
Commodity Contracts [Member]    
Derivative [Line Items]    
Deferred net losses, net of tax, included in AOCI 911  
Cash Flow Hedging [Member] | Commodity Contracts [Member] | Long [Member]    
Derivative [Line Items]    
Open option contracts written, at fair value $ 32,000  
Time period for open copper future contract purchases 14 months  
Fair value of future contracts with net loss position $ 1,300  
Fair Value Hedging [Member] | Commodity Contracts [Member] | Short [Member]    
Derivative [Line Items]    
Fair value of future contracts with net loss position (90)  
Open future contracts to sell copper $ 2,600  
Time period for open copper future contract sales 4 months