Fair Value Accounting - Aggregate Difference Between Fair Value and UPB for Fair Value Option Loans (Details) - USD ($) $ in Millions |
Jun. 30, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Fair Value Disclosures [Abstract] | ||
| Fair Value, option, loans held as assets, current through 89 days | $ 3,528 | $ 2,846 |
| UPB, option, loans held as assets, current through 89 days | 3,421 | 2,744 |
| Fair value, option, loans held as assets, current through 89 days, aggregate difference | 107 | 102 |
| Fair Value, 90 days or more delinquent | 696 | 518 |
| UPB, op days or more delinquent | 676 | 501 |
| Aggregated difference, 90 days or more delinquent | 20 | 17 |
| Loans held-for-sale, fair value | 4,224 | 3,364 |
| Financing receivable, UPB | 4,097 | 3,245 |
| Fair value option, aggregate difference | $ 127 | $ 119 |