Employee Share-based Incentives - Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Cost of prior grants of RSUs, stock appreciation rights (“SARs”) and performance share units (“PSUs”) that are amortized over their applicable vesting periods	$ 276	$ 290	$ 674	$ 600
Accrual of estimated costs of share-based awards to be granted in future periods including those to full-career eligible employees	304	235	612	526
Total noncash compensation expense related to employee share-based incentive plans	$ 580	$ 525	$ 1,286	$ 1,126