Fair Value Option - Gains and Losses on Other Financial Assets and Financial Liabilities at Fair Value (Detail) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2021 |
Jun. 30, 2020 |
Jun. 30, 2021 |
Jun. 30, 2020 |
|
| Fair Value, Option, Quantitative Disclosures [Line Items] | ||||
| Fair Value Option Gains/(Losses) | $ (2,500) | $ (4,859) | $ (3,583) | $ 1,012 |
| Unsecured Short-Term Borrowings Including Current Portion of Unsecured Long-Term Borrowings at Fair Value [Member] | ||||
| Fair Value, Option, Quantitative Disclosures [Line Items] | ||||
| Fair Value Option Gains/(Losses) | (850) | (2,352) | (1,810) | 2,129 |
| Unsecured Long-Term Borrowings at Fair Value [Member] | ||||
| Fair Value, Option, Quantitative Disclosures [Line Items] | ||||
| Fair Value Option Gains/(Losses) | (1,473) | (2,015) | (1,702) | (1,023) |
| Fair Value Option Other [Member] | ||||
| Fair Value, Option, Quantitative Disclosures [Line Items] | ||||
| Fair Value Option Gains/(Losses) | $ (177) | $ (492) | $ (71) | $ (94) |