Employee Incentive Plans - Employee Service Share-based Compensation, Tax Benefit from Compensation Expense (Detail) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
|
| Disclosure of Compensation Related Costs, Share-based Payments [Abstract] | |||
| Share-based compensation | $ 1,985 | $ 2,120 | $ 1,850 |
| Excess net tax benefit for options exercised | 64 | ||
| Excess net tax benefit for share-based awards | $ 120 | $ 63 | $ 269 |