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Pension and Other Postretirement Benefits - Schedule of Fair Value of Pension Plan Assets (Details) - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |  |
Net receivables which represents assets related to divested businesses to be transferred to the buyers |  | $ 1 |
Net payables which represents assets related to divested businesses to be transferred to the buyers | $ 7 |  |
Pension benefits paid |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 4,868 | 4,334 | $ 4,862
Defined benefit plan, alternative investments, fair value of plan asset | 2,880 | 2,726 |
Net plan assets excluding certain net receivables | 4,875 | 4,333 |
Pension benefits paid | Equities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 1,513 | 1,275 |
Defined benefit plan, alternative investments, fair value of plan asset | 923 | 957 |
Pension benefits paid | Equity securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 1,098 | 896 |
Defined benefit plan, alternative investments, fair value of plan asset | 508 | 578 |
Pension benefits paid | Long/short equity hedge funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 260 | 232 |
Defined benefit plan, alternative investments, fair value of plan asset | 260 | 232 |
Pension benefits paid | Private equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 155 | 147 |
Defined benefit plan, alternative investments, fair value of plan asset | 155 | 147 |
Pension benefits paid | Fixed income |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 2,448 | 2,074 |
Defined benefit plan, alternative investments, fair value of plan asset | 1,147 | 922 |
Pension benefits paid | Intermediate and long duration government/credit |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 2,171 | 1,904 |
Defined benefit plan, alternative investments, fair value of plan asset | 1,003 | 770 |
Pension benefits paid | Other |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 277 | 170 |
Defined benefit plan, alternative investments, fair value of plan asset | 144 | 152 |
Pension benefits paid | Other investments |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 914 | 984 |
Defined benefit plan, alternative investments, fair value of plan asset | 810 | 847 |
Pension benefits paid | Real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 269 | 245 |
Defined benefit plan, alternative investments, fair value of plan asset | 165 | 164 |
Pension benefits paid | Discretionary and systematic macro hedge funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 405 | 471 |
Defined benefit plan, alternative investments, fair value of plan asset | 405 | 471 |
Pension benefits paid | Other |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 240 | 268 |
Defined benefit plan, alternative investments, fair value of plan asset | 240 | 212 |
Pension benefits paid | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 941 | 664 |
Pension benefits paid | Level 1 | Equities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 590 | 318 |
Pension benefits paid | Level 1 | Equity securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 590 | 318 |
Pension benefits paid | Level 1 | Long/short equity hedge funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 0 | 0 |
Pension benefits paid | Level 1 | Private equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 0 | 0 |
Pension benefits paid | Level 1 | Fixed income |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 247 | 209 |
Pension benefits paid | Level 1 | Intermediate and long duration government/credit |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 121 | 200 |
Pension benefits paid | Level 1 | Other |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 126 | 9 |
Pension benefits paid | Level 1 | Other investments |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 104 | 137 |
Pension benefits paid | Level 1 | Real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 104 | 81 |
Pension benefits paid | Level 1 | Discretionary and systematic macro hedge funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 0 | 0 |
Pension benefits paid | Level 1 | Other |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 0 | 56 |
Pension benefits paid | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 1,054 | 943 |
Pension benefits paid | Level 2 | Equities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 0 | 0 |
Pension benefits paid | Level 2 | Equity securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 0 | 0 |
Pension benefits paid | Level 2 | Long/short equity hedge funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 0 | 0 |
Pension benefits paid | Level 2 | Private equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 0 | 0 |
Pension benefits paid | Level 2 | Fixed income |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 1,054 | 943 |
Pension benefits paid | Level 2 | Intermediate and long duration government/credit |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 1,047 | 934 |
Pension benefits paid | Level 2 | Other |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 7 | 9 |
Pension benefits paid | Level 2 | Other investments |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 0 | 0 |
Pension benefits paid | Level 2 | Real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 0 | 0 |
Pension benefits paid | Level 2 | Discretionary and systematic macro hedge funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | 0 | 0 |
Pension benefits paid | Level 2 | Other |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of pension and other postretirement plans' assets | $ 0 | $ 0 |

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