| **Non-Insurance Revenues from Contracts with Customers** | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
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| **Revenue from Contract with Customer [Abstract]**       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
| Non-Insurance Revenues from Contracts with Customers     | Non-Insurance Revenues from Contracts with CustomersThe Company had a deferred non-insurance warranty revenue balance of $4.6 billion and $4.7 billion reported under Liabilities as of September 30, 2024 and December 31, 2023.  For the three and nine months ended September 30, 2024, the Company recognized $0.3 billion and $1.1 billion of revenues in each period that were included in the deferred revenue balance as of January 1, 2024.  For the three and nine months ended September 30, 2023, the Company recognized $0.2 billion and $0.9 billion of revenues that were included in the deferred revenue balance as of January 1, 2023.  For the three and nine months ended September 30, 2024 and 2023, non-insurance warranty revenue recognized from performance obligations related to prior periods due to a change in estimate was not material.  The Company expects to recognize approximately $0.4 billion of the deferred revenue in the remainder of 2024, $1.3 billion in 2025, $1.0 billion in 2026 and $1.9 billion thereafter. |

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No definition available.
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| - Definition
The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.
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