Insurance Liabilities - Discounting of Reserves (Details) - USD ($) $ in Millions |
9 Months Ended | 12 Months Ended |
|---|---|---|
Sep. 30, 2026 |
Dec. 31, 2025 |
|
| Discounting of Reserves [Line Items] | ||
| U.S. workers' compensation | $ 1,992 | $ 2,063 |
| Retroactive reinsurance | (765) | (891) |
| Total reserve discount | 1,227 | 1,172 |
| Fortitude RE | ||
| Discounting of Reserves [Line Items] | ||
| Total reserve discount | $ 676 | $ 693 |
| Discount ceded on sale (as a percent) | 100.00% | 100.00% |
| United Kingdom | ||
| Discounting of Reserves [Line Items] | ||
| Total reserve discount | $ 141 | $ 166 |