Derivative Financial Instruments - Amounts Related to Derivative Instruments Not Designated as Hedges (Details) - Not designated as hedges - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax Gain (Loss) Recognized in Income	$ (15)	$ 46	$ (56)	$ 20
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	10	16	25	27
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	6	(3)	13	(5)
Mortgage banking | Interest rate contracts | Mortgage banking income
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax Gain (Loss) Recognized in Income	(8)	10	(4)	(5)
MSRs | Interest rate contracts | Mortgage banking income
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax Gain (Loss) Recognized in Income	$ (23)	$ 23	$ (90)	$ 3