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Derivatives, Hedging Programs and Other Financial Instruments, Notional Quantity Table (Details) mmlbs in Millions | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 mmlbs MMBTU
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Designated as Hedging Instrument | Alloy Metal Hedge | Purchase |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Derivative Notional Amount (Non-Monetary) |  |  |  |  |  | 16.3
Not Designated as Hedging Instrument | Natural Gas Member | Purchase |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Derivative Notional Amount (Non-Monetary) | MMBTU |  |  |  |  |  | 8,580,000
Not Designated as Hedging Instrument | Aluminum | Purchase |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Derivative Notional Amount (Non-Monetary) |  |  |  |  |  | 105.2
Not Designated as Hedging Instrument | Aluminum | Sale |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Derivative Notional Amount (Non-Monetary) |  |  |  |  |  | 0.7
Not Designated as Hedging Instrument | Midwest premium swap contracts | Purchase |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Derivative Notional Amount (Non-Monetary) |  |  |  |  |  | 87.8
Not Designated as Hedging Instrument | Foreign Exchange Contract | Purchase |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Derivative Notional Amount (Non-Monetary) | MMBTU |  |  |  |  |  | 889,155
Not Designated as Hedging Instrument | Electricity | Purchase |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Derivative Notional Amount (Non-Monetary) | MMBTU |  |  |  |  |  | 482,280
Scenario, Forecast | Natural Gas Member |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Derivative, Nonmonetary Notional Amount, Percent of Required Need, Coverage | 77.00% | 83.00% | 83.00% | 78.00% | 80.00% |
Scenario, Forecast | Electricity |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Derivative, Nonmonetary Notional Amount, Percent of Required Need, Coverage |  |  | 9.00% | 55.00% | 55.00% |

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- Definition Nominal number of units used to calculate payment on derivative. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959 + Details
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