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PENSION AND OTHER POSTEMPLOYMENT BENEFITS - Components of Net Periodic Benefit Costs (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2023 | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Pension |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Service cost |  | $ 140 | $ 139 | $ 184
Interest cost |  | 398 | 428 | 273
Expected return on plan assets |  | (530) | (570) | (657)
Amortization of prior service costs (credits) |  | 2 | 2 | 2
Special termination benefits |  | 0 | 21 | 0
Pension & OPEB mark-to-market | $ (59) | 66 | 108 | (98)
Net periodic benefit costs (credits) |  | 76 | 128 | (296)
OPEB |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Service cost |  | 3 | 2 | 3
Interest cost |  | 20 | 21 | 11
Expected return on plan assets |  | (35) | (31) | (39)
Amortization of prior service costs (credits) |  | (1) | (8) | (11)
Special termination benefits |  | 0 | 8 | 0
Pension & OPEB mark-to-market |  | (44) | (30) | 26
Net periodic benefit costs (credits) |  | $ (57) | $ (38) | $ (10)

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