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Derivatives, Hedging Programs and Other Financial Instruments - Summary of (Gain) Loss Associated with Derivative Contracts (Details) - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2025 | Mar. 31, 2024
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Total of income and expense line items presented in our Statements of Consolidated Income in which the effects of cash flow hedges are recorded |  | $ 673.4 | $ 651.3 | [1]
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] |  | Total of income and expense line items presented in our Statements of Consolidated Income in which the effects of cash flow hedges are recorded | Total of income and expense line items presented in our Statements of Consolidated Income in which the effects of cash flow hedges are recorded |
Cash Flow Hedges |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Total of income and expense line items presented in our Statements of Consolidated Income in which the effects of cash flow hedges are recorded |  | $ 673.4 | $ 651.3 | [2]
Cash Flow Hedges | Designated as Hedging Instrument |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Loss (gain) recognized in our Statements of Consolidated Income |  | (5.5) | 2.1 | [2]
Cash Flow Hedges | Designated as Hedging Instrument | Aluminum |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Loss (gain) recognized in our Statements of Consolidated Income |  | (5.2) | 2.0 | [2]
Cash Flow Hedges | Designated as Hedging Instrument | Alloying Metals |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Loss (gain) recognized in our Statements of Consolidated Income |  | (0.4) |  |
Cash Flow Hedges | Designated as Hedging Instrument | Foreign exchange contracts |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Loss (gain) recognized in our Statements of Consolidated Income |  | $ 0.1 |  |
Cash Flow Hedges | Designated as Hedging Instrument | Natural Gas |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Loss (gain) recognized in our Statements of Consolidated Income | [2] |  | 0.3 |
Cash Flow Hedges | Designated as Hedging Instrument | Electricity |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Loss (gain) recognized in our Statements of Consolidated Income | [2] |  | $ (0.2) |
[1] | Adjusted to reflect the retrospective change in inventory valuation methodology from LIFO to WAC. See Note 14 for further discussion.
[2] | Adjusted to reflect the retrospective change in inventory valuation methodology from LIFO to WAC. See Note 14 for further discussion.

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