Financial Derivatives (Impact of Fair Value Hedge Accounting on the Carrying Value of Hedged Items) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Carrying Value of Available-for-sale Securities	$ 61,211	$ 57,618
Carrying Value of Borrowed funds	57,955	$ 59,088
Investment Securities [Member] \| Fair Value Hedging [Member] \| Designated as Hedging Instruments under GAAP [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Carrying Value of Available-for-sale Securities	7,056
Cumulative Fair Value Hedge Adjustment included in Carrying Value of Hedged Items	(230)
Borrowed Funds [Member] \| Fair Value Hedging [Member] \| Designated as Hedging Instruments under GAAP [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Carrying Value of Borrowed funds	28,284
Cumulative Fair Value Hedge Adjustment included in Carrying Value of Hedged Items	(686)
Borrowed Funds Discontinued Relationships [Member] \| Fair Value Hedging [Member] \| Designated as Hedging Instruments under GAAP [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Cumulative Fair Value Hedge Adjustment included in Carrying Value of Hedged Items	$ 600

Increase (Decrease) in Cumulative Fair Value Hedge Adjustment

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- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
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- Definition

Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13,16)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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