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Pension and Other Postretirement Benefit Plans - Fair Values of Other Postretirement Benefit Plan Assets (Details) - Other Postretirement Benefits - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | $ 1,040 | $ 1,045 | $ 947
Cash and cash equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 5 | 13 |
Developed markets equities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 49 | 301 |
Emerging markets equities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 24 | 80 |
Real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 3 | 12 |
Developed markets |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 41 | 223 |
Corporate obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 598 | 157 |
Government and agency obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 266 | 245 |
Mortgage and asset-backed securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 54 | 2 |
Derivatives |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 12 |
Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 44 | 259 |
Level 1 | Cash and cash equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
Level 1 | Developed markets equities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 3 | 24 |
Level 1 | Emerging markets equities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
Level 1 | Real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
Level 1 | Developed markets |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 41 | 223 |
Level 1 | Corporate obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
Level 1 | Government and agency obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
Level 1 | Mortgage and asset-backed securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
Level 1 | Derivatives |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 12 |
Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 918 | 404 |
Level 2 | Cash and cash equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
Level 2 | Developed markets equities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
Level 2 | Emerging markets equities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
Level 2 | Real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
Level 2 | Developed markets |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
Level 2 | Corporate obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 598 | 157 |
Level 2 | Government and agency obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 266 | 245 |
Level 2 | Mortgage and asset-backed securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 54 | 2 |
Level 2 | Derivatives |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
Level 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
Level 3 | Cash and cash equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
Level 3 | Developed markets equities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
Level 3 | Emerging markets equities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
Level 3 | Real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
Level 3 | Developed markets |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
Level 3 | Corporate obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
Level 3 | Government and agency obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
Level 3 | Mortgage and asset-backed securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
Level 3 | Derivatives |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
NAV |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 78 | 382 |
NAV | Cash and cash equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 5 | 13 |
NAV | Developed markets equities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 46 | 277 |
NAV | Emerging markets equities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 24 | 80 |
NAV | Real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 3 | 12 |
NAV | Developed markets |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value |  | 0 |
NAV | Corporate obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value |  | 0 |
NAV | Government and agency obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value |  | 0 |
NAV | Mortgage and asset-backed securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 0 | 0 |
NAV | Derivatives |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | $ 0 | $ 0 |

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