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Long-term and Short-term Debt (Long-term and Short-term Outstanding) (Details) - USD ($) $ in Millions | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | ---
Debt Instrument [Line Items] |  |
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net | $ (108) | $ (87)
Finance Lease, Liability | 32 | 56
Long Term Debt Excluding Consolidated Securitization Entities Face Value | 15,656 | 14,734
Long-term debt | 15,548 | 14,647
Short-term debt | 119 | 175
Debt And Capital Lease Obligations Face Value | 15,775 | 14,909
Total | $ 15,667 | $ 14,822
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 | 14,622 | 13,671
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net | (106) | (83)
Long-term Debt | $ 14,516 | 13,588
Debt Instrument, Interest Rate, Stated Percentage | 5.70% |
Surplus notes |  |
Debt Instrument [Line Items] |  |
Debt Instrument, Principal Outstanding | $ 507 | 507
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net | 0 | (1)
Long-term Debt | 507 | 506
Other notes |  |
Debt Instrument [Line Items] |  |
Debt Instrument, Principal Outstanding | 495 | 500
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net | (2) | (3)
Long-term Debt | 493 | 497
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 | 7.63% |
Minimum | Other notes |  |
Debt Instrument [Line Items] |  |
Debt Instrument, Interest Rate, Effective Percentage | 2.03% |
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 | 7.88% |
Maximum | Other notes |  |
Debt Instrument [Line Items] |  |
Debt Instrument, Interest Rate, Effective Percentage | 8.43% |
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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