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PENSIONS AND OTHER POSTRETIREMENT BENEFITS - Contributions (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022
Pension Benefits |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Employer contributions | $ 29 | $ 6
Pension benefits, employer contributions and payments | 29 |
Expected employer contributions, next fiscal year | 122 |
OPEB |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Employer contributions | 65 | 198
Employer contributions | 65 | 198
Expected employer contributions, next fiscal year | 66 |
OPEB | VEBA |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Employer contributions | 0 | 85
Expected employer contributions, next fiscal year | 0 |
OPEB | Direct Payments |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Employer contributions | 65 | $ 113
Expected employer contributions, next fiscal year | $ 66 |

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