Derivative Financial Instruments - Amounts Related to Derivative Instruments Not Designated as Hedges (Details) - Not designated as hedges - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax Gain (Loss) Recognized in Income	$ (17)	$ 23	$ (73)	$ 43
Client-related and other risk management | Interest rate contracts | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax Gain (Loss) Recognized in Income	11	11	36	38
Client-related and other risk management | Foreign exchange contracts | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax Gain (Loss) Recognized in Income	1	5	14	0
Mortgage banking | Interest rate contracts | Mortgage banking income
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax Gain (Loss) Recognized in Income	7	(3)	3	(8)
MSRs | Interest rate contracts | Mortgage banking income
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax Gain (Loss) Recognized in Income	$ (36)	$ 10	$ (126)	$ 13