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Pension, Postretirement And Other Employee Benefit Plans - Pension and Other Postretirement Plan Assets (Details) - USD ($) $ in Millions | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
--- | --- | --- | ---
Level 3 |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | $ 322 | $ 333 | $ 435
Pension Benefits |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 3,599 | 3,467 | 4,626
Pension Benefits | Level 1 |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 87 | 64 |
Pension Benefits | Level 2 |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 501 | 569 |
Pension Benefits | Level 3 |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 276 | 285 |
Pension Benefits | Assets Measured at NAV |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 2,735 | 2,549 |
Pension Benefits | Equity securities funds |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 1,265 | 1,183 |
Pension Benefits | Equity securities funds | Level 1 |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 74 | 58 |
Pension Benefits | Equity securities funds | Level 2 |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 3 | 26 |
Pension Benefits | Equity securities funds | Level 3 |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 134 | 114 |
Pension Benefits | Equity securities funds | Assets Measured at NAV |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 1,054 | 985 |
Pension Benefits | Fixed-income securities |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 1,325 | 1,316 |
Pension Benefits | Fixed-income securities | Level 1 |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 0 | 0 |
Pension Benefits | Fixed-income securities | Level 2 |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 411 | 527 |
Pension Benefits | Fixed-income securities | Level 3 |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 3 | 5 |
Pension Benefits | Fixed-income securities | Assets Measured at NAV |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 911 | 784 |
Pension Benefits | Alternatives |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 779 | 887 |
Pension Benefits | Alternatives | Level 1 |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 0 | 0 |
Pension Benefits | Alternatives | Level 2 |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 0 | 0 |
Pension Benefits | Alternatives | Level 3 |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 136 | 161 |
Pension Benefits | Alternatives | Assets Measured at NAV |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 643 | 726 |
Pension Benefits | Other investments |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 230 | 81 |
Pension Benefits | Other investments | Level 1 |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 13 | 6 |
Pension Benefits | Other investments | Level 2 |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 87 | 16 |
Pension Benefits | Other investments | Level 3 |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 3 | 5 |
Pension Benefits | Other investments | Assets Measured at NAV |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 127 | 54 |
Other Postretirement Benefits |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 46 | 48 | $ 49
Other Postretirement Benefits | Deposit administration fund |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 46 | 48 |
Other Postretirement Benefits | Deposit administration fund | Level 1 |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 0 | 0 |
Other Postretirement Benefits | Deposit administration fund | Level 2 |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 0 | 0 |
Other Postretirement Benefits | Deposit administration fund | Level 3 |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | 46 | 48 |
Other Postretirement Benefits | Deposit administration fund | Assets Measured at NAV |  |  |
Defined Benefit Plan, Plan Assets, Category [Line Items] |  |  |
Fair value of plan assets | $ 0 | $ 0 |

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