Unsecured Borrowings - Subordinated Long-Term Borrowings (Detail) - USD ($) $ in Millions |
Dec. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Debt Instrument [Line Items] | ||
| Total subordinated Long-term Borrowings, par amount | $ 15,104 | $ 15,017 |
| Total subordinated Long-term Borrowings | $ 19,959 | $ 18,308 |
| Effective weighted average interest rate on long-term subordinated borrowings, after hedging | 1.80% | 3.42% |
| Subordinated Debt [Member] | ||
| Debt Instrument [Line Items] | ||
| Long-term debt, par amount | $ 14,136 | $ 14,041 |
| Long-term subordinated debt outstanding | $ 18,529 | $ 16,980 |
| Effective weighted average interest rate of long-term subordinated debt, after hedging | 1.83% | 3.46% |
| Junior Subordinated Debt [Member] | ||
| Debt Instrument [Line Items] | ||
| Long-term debt, par amount | $ 968 | $ 976 |
| Long-term junior subordinated debt | $ 1,430 | $ 1,328 |
| Effective weighted average interest rate of long-term junior subordinated debt, after hedging | 1.32% | 2.85% |