Derivative Instruments and Hedging Activities (Derivatives Not Designated as Hedges) (Details) - Derivatives not designated as hedging instruments - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Other Noninterest Income/(Expense)	$ 16	$ 20	$ 39	$ 37
Customer-facing interest rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Other Noninterest Income/(Expense)	(5)	4	(100)	350
Offsetting interest rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Other Noninterest Income/(Expense)	12	9	129	(343)
Other interest rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Other Noninterest Income/(Expense)	3	3	(7)	14
Foreign exchange derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Other Noninterest Income/(Expense)	$ 6	$ 4	$ 17	$ 16