Financial Derivatives (Gains (Losses) Recognized on Fair Value and Cash Flow Hedges in the Consolidated Income Statement) (Details) - 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]
Loans	$ 2,345	$ 2,040	$ 4,573	$ 3,944
Investment Securities	557	495	1,069	988
Borrowed Funds	408	273	752	513
Other	334	304	579	605
Fair Value Hedging [Member] \| Designated as Hedging Instrument [Member] \| Interest Rate Contracts [Member] \| Borrowed Funds [Member] \| Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Hedged items	100	(75)	470	11
Derivatives	(125)	67	(495)	(28)
Amounts related to interest settlements on derivatives	7	61	33	137
Fair Value Hedging [Member] \| Designated as Hedging Instrument [Member] \| Interest Rate Contracts [Member] \| Investment Securities [Member] \| Interest Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Hedged items	(24)	33	(114)	12
Derivatives	27	(34)	119	(12)
Amounts related to interest settlements on derivatives	1	(10)	(2)	(25)
Cash Flow Hedging [Member] \| Designated as Hedging Instrument [Member] \| Interest Rate Contracts [Member] \| Loans [Member] \| Interest Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of derivative gains (losses) reclassified from accumulated OCI	11	44	37	90
Cash Flow Hedging [Member] \| Designated as Hedging Instrument [Member] \| Interest Rate Contracts [Member] \| Other [Member] \| Noninterest Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of derivative gains (losses) reclassified from accumulated OCI	5		7	3
Cash Flow Hedging [Member] \| Designated as Hedging Instrument [Member] \| Interest Rate Contracts [Member] \| Investment Securities [Member] \| Interest Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of derivative gains (losses) reclassified from accumulated OCI	$ 3	$ 5	$ 7	$ 11

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Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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