Trading Cash Instruments - Additional Information (Detail) - Trading Cash Instruments Assets Fair Value Disclosure [Member] - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2021 |
Sep. 30, 2020 |
Sep. 30, 2021 |
Sep. 30, 2020 |
|
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ||||
| Net gains / (losses) on assets | $ 38 | $ 49 | $ 127 | $ (87) |
| Net realized gains / (losses) on assets | 27 | 15 | 63 | 59 |
| Net unrealized gains / (losses) on assets relating to instruments still held at the reporting date | 11 | 34 | 64 | (146) |
| Market making [Member] | ||||
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ||||
| Net gains / (losses) on assets | 17 | 25 | 63 | (171) |
| Interest Income [Member] | ||||
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ||||
| Net gains / (losses) on assets | $ 21 | $ 24 | $ 64 | $ 84 |