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Financial Instruments and Derivatives - Additional Information (Details) $ in Thousands, MMBTU in Millions | 3 Months Ended |  |  |
--- | --- | --- | --- | ---
Mar. 31, 2019 USD ($) MMBTU T | Apr. 01, 2018 USD ($) | Jan. 01, 2019 USD ($) | Dec. 31, 2018 USD ($) | Jan. 01, 2018 USD ($)
Derivative [Line Items] |  |  |  |  |
Impact of new accounting pronouncements |  |  | $ (6,771) |  | $ 1,721
Fair value of commodity cash flow hedges, gain (loss) | $ (914) |  |  | $ (1,571) |
Commodity gain (loss) expected to be reclassified to the income statement during the next 12 months | (918) |  |  |  |
Fair value of foreign currency cash flow hedges, gain (loss) | 155 |  |  | (1,624) |
Foreign currency gain (loss) expected to be reclassified to the income statement during the next 12 months | 155 |  |  |  |
Total fair value of other derivatives not designated as hedging instruments | $ (164) |  |  | 166 |
Natural Gas Swaps |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Approximate amount of commodity covered by swap contracts outstanding (in MMBTUs) | MMBTU | 6.0 |  |  |  |
Anticipated usage percentage covered by a swap contract for the current fiscal year | 74.00% |  |  |  |
Anticipated usage percentage covered by a swap contract for the second succeeding fiscal year | 42.00% |  |  |  |
Aluminum Swaps |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Anticipated usage percentage covered by a swap contract for the current fiscal year | 51.00% |  |  |  |
Approximate amount of commodity covered by swap contracts outstanding (in tons) | T | 3,062 |  |  |  |
Foreign Exchange Forward For Construction In Progress |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Net position of contracts | $ (57) |  |  | $ (88) |
Retained Earnings |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Impact of new accounting pronouncements |  |  | $ (6,771) |  | 1,897
Accumulated Other Comprehensive Loss |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Impact of new accounting pronouncements |  |  |  |  | $ (176)
Accumulated Other Comprehensive Loss | Fixed Assets |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Amounts reclassified from accumulated other comprehensive loss | $ (45) | $ (45) |  |  |

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