Insurance Liabilities - Net Loss Reserve Discount Benefit (Charge) (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
Sep. 30, 2026 |
Sep. 30, 2025 |
|
| Net Loss Reserve Discount Benefit (Charge) [Line Items] | ||||
| Current accident year | $ 22 | $ 36 | $ 60 | $ 92 |
| Accretion and other adjustments to prior year discount | (113) | (34) | (131) | (119) |
| Net reserve discount benefit (charge) | (91) | 2 | (71) | (27) |
| Change in discount on loss reserves ceded under retroactive reinsurance | 54 | 7 | 126 | 27 |
| Net change in total reserve discount | (37) | 9 | 55 | 0 |
| United Kingdom | ||||
| Net Loss Reserve Discount Benefit (Charge) [Line Items] | ||||
| Net change in total reserve discount | $ (22) | $ (35) | $ (25) | $ (18) |