Unsecured Borrowings - Unsecured Long-Term Borrowings (Detail) - USD ($) $ in Millions |
Sep. 30, 2021 |
Dec. 31, 2020 |
|---|---|---|
| Debt Instrument [Line Items] | ||
| Fixed-rate obligations | $ 162,850 | $ 139,317 |
| Floating-rate obligations | 79,930 | 74,164 |
| Total | 242,780 | 213,481 |
| U.S. Dollar [Member] | ||
| Debt Instrument [Line Items] | ||
| Fixed-rate obligations | 117,469 | 100,558 |
| Floating-rate obligations | 49,286 | 42,019 |
| Total | 166,755 | 142,577 |
| Non-U.S. Dollar [Member] | ||
| Debt Instrument [Line Items] | ||
| Fixed-rate obligations | 45,381 | 38,759 |
| Floating-rate obligations | 30,644 | 32,145 |
| Total | $ 76,025 | $ 70,904 |