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CAPITAL STOCK - Narrative (Details) $ / shares in Units, $ in Millions |  | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Nov. 01, 2024 $ / shares shares | Dec. 31, 2024 USD ($) shares | Dec. 31, 2023 USD ($) shares | Dec. 31, 2022 USD ($) shares | Nov. 01, 2024 $ / shares | Apr. 22, 2024 USD ($) | Feb. 10, 2022 USD ($)
Class of Stock [Line Items] |  |  |  |  |  |  |
Authorized amount of stock repurchase | $ |  |  |  |  |  | $ 1,500 | $ 1,000
Repurchase of common shares | $ |  | $ 733 | $ 152 | $ 240 |  |  |
Remaining authorized purchase amount | $ |  | $ 1,400 |  |  |  |  |
Common Stock |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Common stock repurchases (in shares) |  | 37,900,000 | 10,400,000 | 12,500,000 |  |  |
Common Shares in Treasury |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Repurchase of common shares | $ |  | $ 733 | $ 152 |  |  |  |
Stelco Holdings Inc |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Share price (in dollars per share) | (per share) | $ 60.00 |  |  |  | $ 13.27 |  |
Common stock per share | 25,862,021 |  |  |  |  |  |
Acquisition (in shares) |  | 25.9 |  |  |  |  |
Stock Issued During Period, Value, Acquisitions | $ |  | $ 343 |  |  |  |  |
Business Acquisition, Shares Exchange Ratio | 0.454 |  |  |  |  |  |
Stelco Holdings Inc | Common Stock |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Acquisition (in shares) |  | 25,900,000 |  |  |  |  |
Stelco Holdings Inc | Common Shares in Treasury |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Stock Issued During Period, Value, Acquisitions | $ |  | $ 473 |  |  |  |  |
Series B Preferred Stock |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Preferred stock authorized (in shares) |  | 4,000,000 |  |  |  |  |
Preferred stock issued (in shares) |  | 0 |  |  |  |  |
Preferred stock outstanding (in shares) |  | 0 |  |  |  |  |
Series A Preferred Stock |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Preferred stock authorized (in shares) |  | 3,000,000 |  |  |  |  |
Preferred stock issued (in shares) |  | 0 |  |  |  |  |
Preferred stock outstanding (in shares) |  | 0 |  |  |  |  |

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