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PENSION AND OTHER POST-EMPLOYMENT BENEFITS - Narrative (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Increase in discount rate |  | 2.21% |  |
Pension |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Expected return on plan assets |  | 7.50% | 7.50% | 7.50%
Expected future contributions in 2025 |  | $ 250 |  |
Expected return on plan assets |  | 657 | $ 652 | $ 618
Actual return on plan assets |  | (1,760) | 625 |
Increase in benefit obligation due to RP2014 mortality table |  | 23 |  |
Pension | Forecast |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Expected return on plan assets | 8.00% |  |  |
Pensions and OPEB |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Expected return on plan assets |  | 696 | 688 | 651
Actual return on plan assets |  | $ (1,830) | $ 689 | $ 1,225
Actual return on plan assets (percent) |  | (19.10%) | 7.90% | 14.70%
OPEB |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Expected return on plan assets |  | 7.50% | 7.50% | 7.50%
Expected return on plan assets |  | $ 39 | $ 36 | $ 33
Actual return on plan assets |  | (70) | 64 |
OPEB | Regulated Transmission |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Mark-to-market adjustment, net of capitalized amounts |  | $ 15 | $ (31) | $ 40

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