INVESTMENT SECURITIES - Schedule of Interest and Dividends on Investment Securities (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
Sep. 30, 2026 |
Sep. 30, 2025 |
|
| Investments [Abstract] | ||||
| Interest income - taxable investment securities | $ 426 | $ 432 | $ 1,210 | $ 1,263 |
| Interest income - nontaxable investment securities | 0 | 1 | 0 | 1 |
| Dividend income - marketable equity securities | 1 | 0 | 2 | 2 |
| Interest on investment securities | $ 427 | $ 433 | $ 1,212 | $ 1,266 |