Financial Derivatives (Gains (Losses) on Derivatives Not Designated As Hedging Instruments under GAAP) (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivative [Line Items]
Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net	$ 90	$ 279	$ 964	$ 374
Mortgage Banking [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net	125	218	779	346
Customer Contracts [Member]
Derivative [Line Items]
Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net	67	71	80	92
Customer Contracts [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net	38	41	40	39
Customer Contracts [Member] | Foreign Exchange And Other Contract [Member]
Derivative [Line Items]
Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net	29	30	40	53
Other Risk Management Activity [Member] | Foreign Exchange And Other Contract [Member]
Derivative [Line Items]
Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net	$ (102)	$ (10)	$ 105	$ (64)