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Long-term and Short-term Debt (Long-term and Short-term Outstanding) (Details) - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Debt Instrument [Line Items] |  |
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net | $ (101) | $ (108)
Finance Lease, Liability | 6 | 32
Long Term Debt Excluding Consolidated Securitization Entities Face Value | 15,187 | 15,656
Long-term debt | 15,086 | 15,548
Short-term debt (includes $133 and $0, respectively, relating to variable interest entities) | 465 | 119
Debt And Capital Lease Obligations Face Value | 15,652 | 15,775
Total | $ 15,551 | $ 15,667
Finance Lease, Liability, Statement of Financial Position [Extensible Enumeration] | Long-term debt | Long-Term Debt and Lease Obligation, Including Current Maturities [Abstract]
Long-term Debt [Member] |  |
Debt Instrument [Line Items] |  |
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net | $ 0 | $ 0
Senior notes |  |
Debt Instrument [Line Items] |  |
Debt Instrument, Principal Outstanding | 14,530 | 14,622
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net | (99) | (106)
Long-term Debt | $ 14,431 | 14,516
Debt Instrument, Interest Rate, Stated Percentage | 5.70% |
Surplus notes |  |
Debt Instrument [Line Items] |  |
Debt Instrument, Principal Outstanding | $ 250 | 507
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net | 0 | 0
Long-term Debt | 250 | 507
Other notes |  |
Debt Instrument [Line Items] |  |
Debt Instrument, Principal Outstanding | 401 | 495
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net | (2) | (2)
Long-term Debt | 399 | 493
Short-term Debt [Member] |  |
Debt Instrument [Line Items] |  |
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net | $ 0 | $ 0
Minimum | Senior notes |  |
Debt Instrument [Line Items] |  |
Debt Instrument, Interest Rate, Effective Percentage | 0.50% |
Minimum | Surplus notes |  |
Debt Instrument [Line Items] |  |
Debt Instrument, Interest Rate, Effective Percentage | 7.80% |
Minimum | Other notes |  |
Debt Instrument [Line Items] |  |
Debt Instrument, Interest Rate, Effective Percentage | 5.58% |
Maximum | Senior notes |  |
Debt Instrument [Line Items] |  |
Debt Instrument, Interest Rate, Effective Percentage | 6.50% |
Maximum | Surplus notes |  |
Debt Instrument [Line Items] |  |
Debt Instrument, Interest Rate, Effective Percentage | 7.80% |
Maximum | Other notes |  |
Debt Instrument [Line Items] |  |
Debt Instrument, Interest Rate, Effective Percentage | 8.39% |
Committed Credit Facility Six [Member] |  |
Debt Instrument [Line Items] |  |
Line of Credit Facility, Maximum Borrowing Capacity | $ 2,896 |
General Credit Facility Three [Member] |  |
Debt Instrument [Line Items] |  |
Line of Credit Facility, Maximum Borrowing Capacity | $ 3,000 |

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