Derivative Instruments and Hedging Activities (Derivatives Not Designated as Hedges) (Details) - Derivatives not designated as hedging instruments - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Other Noninterest Income/(Expense)	$ (2)	$ 2	$ 23	$ 17
Customer-facing interest rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Other Noninterest Income/(Expense)	87	34	(95)	346
Offsetting interest rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Other Noninterest Income/(Expense)	(89)	(39)	117	(352)
Other interest rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Other Noninterest Income/(Expense)	(6)	2	(10)	11
Foreign exchange derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Other Noninterest Income/(Expense)	$ 6	$ 5	$ 11	$ 12