Employee Share-based Incentives - Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Payment Arrangement [Abstract]
Cost of prior grants of RSUs, performance share units (“PSUs”) and stock appreciation rights (“SARs”) that are amortized over their applicable vesting periods	$ 265	$ 282	$ 882	$ 956
Accrual of estimated costs of share-based awards to be granted in future periods including those to full-career eligible employees	294	240	900	852
Total noncash compensation expense related to employee share-based incentive plans	$ 559	$ 522	$ 1,782	$ 1,808