Fair Value Accounting - Aggregate Difference Between Fair Value and UPB for Fair Value Option Loans (Details) - USD ($) $ in Millions |
Mar. 31, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Fair Value Disclosures [Abstract] | ||
| Fair Value, option, loans held as assets, current through 89 days | $ 3,057 | $ 2,846 |
| UPB, option, loans held as assets, current through 89 days | 2,996 | 2,744 |
| Fair value, option, loans held as assets, current through 89 days, aggregate difference | 61 | 102 |
| Fair Value, 90 days or more delinquent | 758 | 518 |
| UPB, op days or more delinquent | 732 | 501 |
| Aggregated difference, 90 days or more delinquent | 26 | 17 |
| Loans held-for-sale, fair value | 3,815 | 3,364 |
| Financing receivable, UPB | 3,728 | 3,245 |
| Fair value option, aggregate difference | $ 87 | $ 119 |