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PENSION AND OTHER POST-EMPLOYMENT BENEFITS - Obligations and Funded Status (Details) - USD ($) $ in Millions |  | 12 Months Ended
--- | --- | ---
Feb. 01, 2019 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Change in fair value of plan assets: |  |  |  |
Company contributions | $ 500 |  |  |
Pension |  |  |  |
Change in benefit obligation: |  |  |  |
Benefit obligation as of January 1 |  | $ 11,050 | $ 9,462 |
Service cost |  | 194 | 193 | $ 224
Interest cost |  | 287 | 373 | 372
Plan participants’ contributions |  | 0 | 0 |
Plan amendments |  | 9 | 2 |
Special termination benefits |  | 0 | 14 |
Medicare retiree drug subsidy |  | 0 | 0 |
Actuarial loss |  | 1,011 | 1,535 |
Benefits paid |  | (616) | (529) |
Benefit obligation as of December 31 |  | 11,935 | 11,050 | 9,462
Change in fair value of plan assets: |  |  |  |
Fair value of plan assets as of January 1 |  | 8,395 | 6,984 |
Actual return on plan assets |  | 1,165 | 1,419 |
Company contributions |  | 24 | 521 |
Plan participants’ contributions |  | 0 | 0 |
Benefits paid |  | (616) | (529) |
Fair value of plan assets as of December 31 |  | 8,968 | 8,395 | 6,984
Funded Status: |  |  |  |
Funded Status (Net liability as of December 31) |  | (2,967) | (2,655) |
Accumulated benefit obligation |  | 11,376 | 10,439 |
Amounts Recognized in AOCI: |  |  |  |
Prior service cost (credit) |  | $ 12 | $ 24 |
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract] |  |  |  |
Discount rate |  | 2.67% | 3.34% |
Rate of compensation increase |  | 4.10% | 4.10% |
Cash balance weighted average interest crediting rate |  | 2.57% | 2.57% |
Allocation of Plan Assets (as of December 31) |  |  |  |
Asset Allocation |  | 100.00% | 100.00% |
Pension | Equity securities |  |  |  |
Allocation of Plan Assets (as of December 31) |  |  |  |
Asset Allocation |  | 23.00% | 29.00% |
Pension | Fixed Income |  |  |  |
Allocation of Plan Assets (as of December 31) |  |  |  |
Asset Allocation |  | 35.00% | 36.00% |
Pension | Hedge funds |  |  |  |
Allocation of Plan Assets (as of December 31) |  |  |  |
Asset Allocation |  | 7.00% | 9.00% |
Pension | Insurance-linked securities |  |  |  |
Allocation of Plan Assets (as of December 31) |  |  |  |
Asset Allocation |  | 4.00% | 2.00% |
Pension | Real estate funds |  |  |  |
Allocation of Plan Assets (as of December 31) |  |  |  |
Asset Allocation |  | 9.00% | 7.00% |
Pension | Derivatives |  |  |  |
Allocation of Plan Assets (as of December 31) |  |  |  |
Asset Allocation |  | 0.00% | 0.00% |
Pension | Private equity funds |  |  |  |
Allocation of Plan Assets (as of December 31) |  |  |  |
Asset Allocation |  | 5.00% | 4.00% |
Pension | Cash and short-term securities |  |  |  |
Allocation of Plan Assets (as of December 31) |  |  |  |
Asset Allocation |  | 17.00% | 13.00% |
Pension | Qualified plan |  |  |  |
Funded Status: |  |  |  |
Funded Status (Net liability as of December 31) |  | $ (2,500) | $ (2,203) |
Pension | Non-qualified plans |  |  |  |
Funded Status: |  |  |  |
Funded Status (Net liability as of December 31) |  | (467) | (452) |
OPEB |  |  |  |
Change in benefit obligation: |  |  |  |
Benefit obligation as of January 1 |  | 654 | 608 |
Service cost |  | 4 | 3 | 5
Interest cost |  | 15 | 22 | 25
Plan participants’ contributions |  | 4 | 4 |
Plan amendments |  | 0 | 0 |
Special termination benefits |  | 0 | 0 |
Medicare retiree drug subsidy |  | 1 | 1 |
Actuarial loss |  | 41 | 64 |
Benefits paid |  | (43) | (48) |
Benefit obligation as of December 31 |  | 676 | 654 | 608
Change in fair value of plan assets: |  |  |  |
Fair value of plan assets as of January 1 |  | 458 | 408 |
Actual return on plan assets |  | 60 | 73 |
Company contributions |  | 23 | 21 |
Plan participants’ contributions |  | 4 | 4 |
Benefits paid |  | (43) | (48) |
Fair value of plan assets as of December 31 |  | 502 | 458 | $ 408
Funded Status: |  |  |  |
Funded Status (Net liability as of December 31) |  | (174) | (196) |
Accumulated benefit obligation |  | 0 | 0 |
Amounts Recognized in AOCI: |  |  |  |
Prior service cost (credit) |  | $ (39) | $ (85) |
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract] |  |  |  |
Discount rate |  | 2.45% | 3.18% |
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) |  | 4.50% | 4.50% |
Allocation of Plan Assets (as of December 31) |  |  |  |
Asset Allocation |  | 100.00% | 100.00% |
OPEB | Equity securities |  |  |  |
Allocation of Plan Assets (as of December 31) |  |  |  |
Asset Allocation |  | 55.00% | 54.00% |
OPEB | Fixed Income |  |  |  |
Allocation of Plan Assets (as of December 31) |  |  |  |
Asset Allocation |  | 28.00% | 30.00% |
OPEB | Hedge funds |  |  |  |
Allocation of Plan Assets (as of December 31) |  |  |  |
Asset Allocation |  | 0.00% | 0.00% |
OPEB | Insurance-linked securities |  |  |  |
Allocation of Plan Assets (as of December 31) |  |  |  |
Asset Allocation |  | 0.00% | 0.00% |
OPEB | Real estate funds |  |  |  |
Allocation of Plan Assets (as of December 31) |  |  |  |
Asset Allocation |  | 0.00% | 0.00% |
OPEB | Private equity funds |  |  |  |
Allocation of Plan Assets (as of December 31) |  |  |  |
Asset Allocation |  | 0.00% | 0.00% |
OPEB | Cash and short-term securities |  |  |  |
Allocation of Plan Assets (as of December 31) |  |  |  |
Asset Allocation |  | 17.00% | 16.00% |
OPEB | Pre Medicare |  |  |  |
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract] |  |  |  |
Health care cost trend rate assumed (pre/post-Medicare) |  | 6.00% | 6.00% |
OPEB | Post Medicare |  |  |  |
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract] |  |  |  |
Health care cost trend rate assumed (pre/post-Medicare) |  | 5.50% | 5.50% |
OPEB | Qualified plan |  |  |  |
Funded Status: |  |  |  |
Funded Status (Net liability as of December 31) |  | $ 0 | $ 0 |
OPEB | Non-qualified plans |  |  |  |
Funded Status: |  |  |  |
Funded Status (Net liability as of December 31) |  | $ 0 | $ 0 |

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