GOODWILL AND INTANGIBLE ASSETS AND LIABILITIES - Goodwill (Details) - USD ($) $ in Millions |
3 Months Ended | 5 Months Ended | ||
|---|---|---|---|---|
Mar. 31, 2025 |
Mar. 31, 2025 |
Dec. 31, 2024 |
Nov. 01, 2024 |
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| Goodwill [Line Items] | Ìý | Ìý | Ìý | Ìý |
| Goodwill | $ 1,767 | $ 1,767 | $ 1,768 | Ìý |
| Stelco Holdings Inc | Ìý | Ìý | Ìý | Ìý |
| Goodwill [Line Items] | Ìý | Ìý | Ìý | Ìý |
| Goodwill | 785 | 785 | Ìý | $ 786 |
| Goodwill, Measurement Period Adjustment | (1) | (1) | Ìý | Ìý |
| Steelmaking [Member] | Ìý | Ìý | Ìý | Ìý |
| Goodwill [Line Items] | Ìý | Ìý | Ìý | Ìý |
| Goodwill | 1,718 | 1,718 | 1,719 | Ìý |
| Other Businesses [Member] | Ìý | Ìý | Ìý | Ìý |
| Goodwill [Line Items] | Ìý | Ìý | Ìý | Ìý |
| Goodwill | $ 49 | $ 49 | $ 49 | Ìý |
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- Definition Amount, after accumulated impairment loss, of asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of increase (decrease) from measurement period adjustment of asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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