Goodwill and Mortgage Servicing Rights - Key Economic Assumptions (Details) - USD ($) $ in Millions |
9 Months Ended | 12 Months Ended |
|---|---|---|
Sep. 30, 2026 |
Dec. 31, 2025 |
|
| Intangible Asset, Goodwill and Other [Abstract] | ||
| Weighted-average prepayment speed assumption (constant prepayment rate) | 6.14% | 6.77% |
| Impact on fair value of 10% adverse change | $ (160) | $ (181) |
| Impact on fair value of 20% adverse change | $ (314) | $ (353) |
| Weighted-average option adjusted spread | 5.73% | 6.14% |
| Impact on fair value of a 100 basis point adverse change | $ (410) | $ (394) |
| Impact on fair value of a 200 basis point adverse change | $ (788) | $ (757) |