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EMPLOYEE BENEFIT PLANS - PLAN ASSETS (Details) - USD ($) $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Qualified Defined Benefit [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 2,488 | $ 2,239 | $ 1,858
Plan asset allocations | 100.00% | 100.00% |
Qualified Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 2,386 | $ 2,126 |
Qualified Defined Benefit [Member] | Fixed Income Securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan asset allocations | 33.00% | 35.00% |
Qualified Defined Benefit [Member] | Credit bond index fund [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 1,088 | $ 1,009 |
Qualified Defined Benefit [Member] | Real Estate [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan asset allocations | 5.00% | 6.00% |
Qualified Defined Benefit [Member] | Real Estate [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 96 | $ 102 |
Qualified Defined Benefit [Member] | Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 6 | $ 11 |
Qualified Defined Benefit [Member] | Defined Benefit Plan, Equity Securities, US |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan asset allocations | 44.00% | 41.00% |
Qualified Defined Benefit [Member] | Defined Benefit Plan, Equity Securities, US | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 914 | $ 773 |
Qualified Defined Benefit [Member] | Defined Benefit Plan, Equity Securities, Non-US |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan asset allocations | 18.00% | 18.00% |
Qualified Defined Benefit [Member] | Defined Benefit Plan, Equity Securities, Non-US | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 384 | $ 344 |
Qualified Defined Benefit Plan - Salaried [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan asset allocations | 100.00% | 100.00% |
Qualified Defined Benefit Plan - Salaried [Member] | Fixed Income Securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan asset allocations | 90.00% | 90.00% |
Qualified Defined Benefit Plan - Salaried [Member] | Real Estate [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan asset allocations | 0.00% | 0.00% |
Qualified Defined Benefit Plan - Salaried [Member] | Defined Benefit Plan, Equity Securities, US |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan asset allocations | 7.00% | 7.00% |
Qualified Defined Benefit Plan - Salaried [Member] | Defined Benefit Plan, Equity Securities, Non-US |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan asset allocations | 3.00% | 3.00% |
Minimum [Member] | Qualified Defined Benefit [Member] | Fixed Income Securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description | 11 |  |
Minimum [Member] | Qualified Defined Benefit [Member] | Real Estate [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description | — |  |
Minimum [Member] | Qualified Defined Benefit [Member] | Defined Benefit Plan, Equity Securities, US |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description | 36 |  |
Minimum [Member] | Qualified Defined Benefit [Member] | Defined Benefit Plan, Equity Securities, Non-US |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description | 13 |  |
Minimum [Member] | Qualified Defined Benefit Plan - Salaried [Member] | Fixed Income Securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description | 85 |  |
Minimum [Member] | Qualified Defined Benefit Plan - Salaried [Member] | Real Estate [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description | — |  |
Minimum [Member] | Qualified Defined Benefit Plan - Salaried [Member] | Defined Benefit Plan, Equity Securities, US |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description | 2 |  |
Minimum [Member] | Qualified Defined Benefit Plan - Salaried [Member] | Defined Benefit Plan, Equity Securities, Non-US |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description | — |  |
Maximum [Member] | Qualified Defined Benefit [Member] | Fixed Income Securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description | 25 |  |
Maximum [Member] | Qualified Defined Benefit [Member] | Real Estate [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description | 10 |  |
Maximum [Member] | Qualified Defined Benefit [Member] | Defined Benefit Plan, Equity Securities, US |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description | 46 |  |
Maximum [Member] | Qualified Defined Benefit [Member] | Defined Benefit Plan, Equity Securities, Non-US |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description | 23 |  |
Maximum [Member] | Qualified Defined Benefit Plan - Salaried [Member] | Fixed Income Securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description | 95 |  |
Maximum [Member] | Qualified Defined Benefit Plan - Salaried [Member] | Real Estate [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description | — |  |
Maximum [Member] | Qualified Defined Benefit Plan - Salaried [Member] | Defined Benefit Plan, Equity Securities, US |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description | 12 |  |
Maximum [Member] | Qualified Defined Benefit Plan - Salaried [Member] | Defined Benefit Plan, Equity Securities, Non-US |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description | 5 |  |

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