Insurance Liabilities - Net Loss Reserve Discount Benefit (Charge) (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Net Loss Reserve Discount Benefit (Charge) [Line Items] | ||||
| Current accident year | $ 15 | $ 33 | $ 38 | $ 56 |
| Accretion and other adjustments to prior year discount | (43) | (45) | (18) | (85) |
| Net reserve discount benefit (charge) | (28) | (12) | 20 | (29) |
| Change in discount on loss reserves ceded under retroactive reinsurance | 19 | 19 | 72 | 20 |
| Net change in total reserve discount | (9) | 7 | 92 | (9) |
| United Kingdom | ||||
| Net Loss Reserve Discount Benefit (Charge) [Line Items] | ||||
| Net change in total reserve discount | $ 1 | $ 11 | $ (3) | $ 17 |