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v3.19.1

Derivatives, Hedging Programs and Other Financial Instruments, Material Derivative Positions (Details) mmlbs in Millions | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | Mar. 31, 2019 MMBTU MWH mmlbs
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Aluminum | Designated as Hedging Instrument | Purchase |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |
Derivative non-monetary notional amount |  |  |  |  |  |  | 117.1
Aluminum | Designated as Hedging Instrument | Sales |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |
Derivative non-monetary notional amount |  |  |  |  |  |  | 0.5
Midwest premium swap contracts | Designated as Hedging Instrument | Purchase |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |
Derivative non-monetary notional amount |  |  |  |  |  |  | 89.4
Alloy Metal Hedge | Designated as Hedging Instrument | Purchase |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |
Derivative non-monetary notional amount |  |  |  |  |  |  | 10.5
Natural Gas | Designated as Hedging Instrument | Purchase |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |
Derivative non-monetary notional amount | MMBTU |  |  |  |  |  |  | 8,530,000
Electricity | Designated as Hedging Instrument | Purchase |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |
Derivative non-monetary notional amount | MWH |  |  |  |  |  |  | 307,080
Scenario, Forecast | Natural Gas |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |
Derivative, Nonmonetary Notional Amount, Percent of Required Need, Coverage | 31.00% | 37.00% | 37.00% | 66.00% | 66.00% | 69.00% |
Scenario, Forecast | Electricity |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |
Derivative, Nonmonetary Notional Amount, Percent of Required Need, Coverage |  |  |  | 27.00% | 54.00% | 54.00% |

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- Definition Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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