The number of satellite recycled aluminum slab centers in aluminum operations.

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Percentage of remaining voting interests to be acquired.

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Percentage of voting equity interest acquired in business combination.

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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As of the reporting date, the aggregate carrying amount of all noncontrolling interests which are redeemable by the (parent) entity (1) at a fixed or determinable price on a fixed or determinable date, (2) at the option of the holder of the noncontrolling interest, or (3) upon occurrence of an event that is not solely within the control of the (parent) entity. This item includes noncontrolling interest holder's ownership (or holders' ownership) regardless of the type of equity interest (common, preferred, other) including all potential organizational (legal) forms of the investee entity.

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Percentage of subsidiary's or equity method investee's stock owned by parent immediately after all stock transactions.

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Description of the Business and Significant Accounting Policies - Description of the Business (Details) $ in Thousands		6 Months Ended	12 Months Ended
	Apr. 01, 2025	Jun. 30, 2025 USD ($) item segment	Dec. 31, 2024 USD ($)
Segment Reporting Information
Number of reportable segments \| segment		4
Redeemable noncontrolling interests		$ 141,226	$ 171,212
United Steel Supply, LLC
Segment Reporting Information
Acquisition of interest (as a percent)	5.00%
Percentage of remaining voting interest to be acquired	5.00%
United Steel Supply, LLC
Segment Reporting Information
Noncontrolling interest, ownership percentage	95.00%	95.00%	90.00%
Redeemable noncontrolling interests		$ 30,000	$ 60,000
SDI Biocarbon Solutions \| Steel Operations
Segment Reporting Information
Noncontrolling interest, ownership percentage		75.00%
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%