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Derivatives, Hedging Programs and Other Financial Instruments - Summary of Derivative Positions (Details) - 3 months ended Mar. 31, 2025 Mmlb in Millions | EUR (€) Mmlb MMBTU | GBP (£) Mmlb MMBTU
--- | --- | ---
Purchase | Aluminum |  |
Derivative [Line Items] |  |
Derivative non-monetary notional amount | 61.0 | 61.0
Purchase | Aluminum | Minimum |  |
Derivative [Line Items] |  |
Derivative maturity period | Apr. 30, 2025 |
Purchase | Aluminum | Maximum |  |
Derivative [Line Items] |  |
Derivative maturity period | Aug. 31, 2026 |
Purchase | Fixed Price Purchase Contracts for MWTP |  |
Derivative [Line Items] |  |
Derivative non-monetary notional amount | 56.5 | 56.5
Purchase | Fixed Price Purchase Contracts for MWTP | Minimum |  |
Derivative [Line Items] |  |
Derivative maturity period | Apr. 30, 2025 |
Purchase | Fixed Price Purchase Contracts for MWTP | Maximum |  |
Derivative [Line Items] |  |
Derivative maturity period | Aug. 31, 2026 |
Purchase | Alloying Metals |  |
Derivative [Line Items] |  |
Derivative non-monetary notional amount | 7.4 | 7.4
Purchase | Alloying Metals | Minimum |  |
Derivative [Line Items] |  |
Derivative maturity period | Apr. 30, 2025 |
Purchase | Alloying Metals | Maximum |  |
Derivative [Line Items] |  |
Derivative maturity period | Dec. 31, 2026 |
Purchase | Natural Gas |  |
Derivative [Line Items] |  |
Derivative non-monetary notional amount | MMBTU | 2,700,000 | 2,700,000
Purchase | Natural Gas | Minimum |  |
Derivative [Line Items] |  |
Derivative maturity period | Apr. 30, 2025 |
Purchase | Natural Gas | Maximum |  |
Derivative [Line Items] |  |
Derivative maturity period | Dec. 31, 2027 |
Purchase | Euro |  |
Derivative [Line Items] |  |
Derivative notional amount | € | € 5,812,634 |
Purchase | Euro | Minimum |  |
Derivative [Line Items] |  |
Derivative maturity period | Apr. 30, 2025 |
Purchase | Euro | Maximum |  |
Derivative [Line Items] |  |
Derivative maturity period | Jul. 31, 2027 |
Purchase | British Pounds |  |
Derivative [Line Items] |  |
Derivative notional amount | £ |  | £ 20,000
Purchase | British Pounds | Minimum |  |
Derivative [Line Items] |  |
Derivative maturity period | Apr. 30, 2025 |
Purchase | British Pounds | Maximum |  |
Derivative [Line Items] |  |
Derivative maturity period | May 31, 2025 |
Sales | Aluminum |  |
Derivative [Line Items] |  |
Derivative non-monetary notional amount | 11.0 | 11.0
Sales | Aluminum | Minimum |  |
Derivative [Line Items] |  |
Derivative maturity period | Apr. 30, 2025 |
Sales | Aluminum | Maximum |  |
Derivative [Line Items] |  |
Derivative maturity period | Dec. 31, 2025 |
Sales | Fixed Price Sale Contracts for MWTP |  |
Derivative [Line Items] |  |
Derivative non-monetary notional amount | 10.9 | 10.9
Derivative maturity period | Apr. 30, 2025 |

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