Employee Share-based Incentives - Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Cost of prior grants of RSUs, performance share units (“PSUs”), stock appreciation rights ("SARs") and stock options that are amortized over their applicable vesting periods	$ 283	$ 249	$ 919	$ 859
Accrual of estimated costs of share-based awards to be granted in future periods, predominantly those to full-career eligible employees	335	272	1,346	1,108
Total noncash compensation expense related to employee share-based incentive plans	$ 618	$ 521	$ 2,265	$ 1,967