Loans - Impaired Financing Receivables (Detail) - USD ($) $ in Millions |
Dec. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Financing Receivable, Impaired [Line Items] | ||
| Nonaccrual loans | $ 3,552 | $ 1,530 |
| Nonaccrual loans divided by gross loans at amortized cost | 3.40% | 1.70% |
| Corporate [Member] | ||
| Financing Receivable, Impaired [Line Items] | ||
| Nonaccrual loans | $ 2,651 | $ 1,122 |
| Wealth management [Member] | ||
| Financing Receivable, Impaired [Line Items] | ||
| Nonaccrual loans | 61 | 52 |
| Commercial real estate [Member] | ||
| Financing Receivable, Impaired [Line Items] | ||
| Nonaccrual loans | 649 | 175 |
| Residential real estate [Member] | ||
| Financing Receivable, Impaired [Line Items] | ||
| Nonaccrual loans | 25 | 143 |
| Installment [Member] | ||
| Financing Receivable, Impaired [Line Items] | ||
| Nonaccrual loans | 44 | $ 38 |
| Other [Member] | ||
| Financing Receivable, Impaired [Line Items] | ||
| Nonaccrual loans | $ 122 |