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Description of the Business and Significant Accounting Policies - Description of the Business (Details) $ in Thousands | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2024 USD ($) item segment | Dec. 31, 2023 USD ($)
Segment Reporting Information |  |
Number of reportable segments | segment | 4 |
Redeemable noncontrolling interests | $ 171,212 | $ 171,212
United Steel Supply, LLC |  |
Segment Reporting Information |  |
Noncontrolling interest, ownership percentage | 90.00% | 90.00%
Redeemable noncontrolling interests | $ 60,000 | $ 60,000
Mesabi Nugget |  |
Segment Reporting Information |  |
Noncontrolling interest, ownership percentage | 86.00% | 86.00%
Redeemable noncontrolling interests | $ 111,200 | $ 111,200
Unity Aluminum, Inc | Aluminum Operations |  |
Segment Reporting Information |  |
Number Of Satellite Recycled Aluminum Slab Centers | item | 2 |
Noncontrolling interest, ownership percentage | 94.40% |

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