Reinsurance and Indemnification - Schedule of Effects of Reinsurance Ceded and Indemnification Programs on Property and Casualty Insurance Claims and Claims Expense and Accident, Health and Other Policy Benefits (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
Sep. 30, 2026 |
Sep. 30, 2025 |
|
| Income Statement Location [Axis]: us-gaap:PolicyholderBenefitsAndClaimsIncurredNet | ||||
| Reductions to costs and expenses due to reinsurance ceded amounts | ||||
| Ceded losses incurred | $ (154) | $ (163) | $ (207) | $ (1,989) |
| Income Statement Location [Axis]: all:AccidentAndHealthInsuranceContractBenefitsNetOfReinsuranceRecoveries | ||||
| Reductions to costs and expenses due to reinsurance ceded amounts | ||||
| Ceded losses incurred | $ (100) | $ (112) | $ (317) | $ (140) |