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Contingencies - Narrative (Details) - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
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Loss Contingencies [Line Items] |  |  |  |
Environmental Loss Contingency, Statement of Financial Position [Extensible Enumeration] | Other Liabilities |  |  |
Reinsurance recoverables on asbestos and environmental reserves, net of allowance | $ 4,957 | $ 4,288 | $ 3,767 | $ 3,419
Property and Casualty Group |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Liability for asbestos and environmental reserves | 494 |  |  |
APU |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Liability for environmental and other claims | 84 |  |  |
GAFRI |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Liability for environmental and other claims | 7 |  |  |
A&E reserves | Property and Casualty Group |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Reinsurance recoverables on asbestos and environmental reserves, net of allowance | $ 135 |  |  |

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