Loss and Loss Adjustment Expense Reserves (Details) - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
|
| Liability for Claims and Claims Adjustment Expense [Line Items] | ||
| Prior years | $ 451 | $ 278 |
| Personal Lines | Personal auto business | ||
| Liability for Claims and Claims Adjustment Expense [Line Items] | ||
| Prior years | 445 | 260 |
| Personal Lines | Personal property | ||
| Liability for Claims and Claims Adjustment Expense [Line Items] | ||
| Prior years | 30 | |
| Short-Duration Insurance Contract, Accident Year 2025 | ||
| Liability for Claims and Claims Adjustment Expense [Line Items] | ||
| Prior years | 320 | |
| Short-Duration Insurance Contract, Accident Year 2024 | ||
| Liability for Claims and Claims Adjustment Expense [Line Items] | ||
| Prior years | $ 115 | 180 |
| Short-Duration Insurance Contract, Accident Year 2023 | ||
| Liability for Claims and Claims Adjustment Expense [Line Items] | ||
| Prior years | $ 90 | |