Other Assets - Other Assets (Parenthetical) (Detail) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
|
| Schedule Of Other Assets [Line Items] | ||
| Accumulated depreciation and amortization | $ 10,120 | $ 9,950 |
| Property, leasehold improvements and equipment used for operation | 6,540 | 6,160 |
| Foreclosed real estate included in property, leasehold improvements and equipment | $ 318 | $ 521 |
| Amortization period - Capitalized costs of software developed or obtained for internal use | 3 years | 3 years |
| Operating lease right-of-use assets | $ 2,280 | $ 2,360 |
| Investments in qualified affordable housing projects | 678 | 606 |
| Tangible asset impairment charges | 171 | |
| Asset Management [Member] | ||
| Schedule Of Other Assets [Line Items] | ||
| Assets classified as held for sale | 437 | 470 |
| European headquarters in London [Member] | ||
| Schedule Of Other Assets [Line Items] | ||
| Operating lease right-of-use assets | $ 182 | $ 963 |