Financial Derivatives (Total Derivatives) (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Derivative Notional Amount	$ 426,509	$ 410,803
Derivative Asset, Fair Value	3,093	4,616
Derivative Liability, Fair Value	2,608	3,839
Derivative Asset, Fair Value Offset Amount	(1,373)	(2,460)
Derivative Asset, Cash Collateral	(397)	(657)
Derivative Asset, Net Fair Value	1,323	1,499
Derivative Liability, Fair Value Offset Amount	(1,373)	(2,460)
Derivative Liability, Cash Collateral	(691)	(484)
Derivative Liability, Net Fair Value	544	895
Increase (Decrease) in Derivative Assets	(800)
Increase (Decrease) in Derivative Liabilities	(700)
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Notional Amount	56,241	55,786
Derivative Asset, Fair Value	248	889
Derivative Liability, Fair Value	115	285
Designated as Hedging Instrument [Member] \| Fair Value Hedging [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	32,820	34,010
Derivative Asset, Fair Value	165	551
Derivative Liability, Fair Value	62	214
Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	22,383	20,831
Derivative Asset, Fair Value	83	313
Derivative Liability, Fair Value	2	71
Designated as Hedging Instrument [Member] \| Net Investment Hedging [Member] \| Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	1,038	945
Derivative Asset, Fair Value		25
Derivative Liability, Fair Value	51
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Notional Amount	370,268	355,017
Derivative Asset, Fair Value	2,845	3,727
Derivative Liability, Fair Value	2,493	3,554
Not Designated as Hedging Instrument [Member] \| Mortgage Banking [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	123,403	130,559
Derivative Asset, Fair Value	377	907
Derivative Liability, Fair Value	170	565
Not Designated as Hedging Instrument [Member] \| Mortgage Banking [Member] \| Swap [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	50,902	49,071
Derivative Asset, Fair Value	337	783
Derivative Liability, Fair Value	141	505
Not Designated as Hedging Instrument [Member] \| Mortgage Banking [Member] \| Future [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	37,396	36,264
Not Designated as Hedging Instrument [Member] \| Mortgage Banking [Member] \| Mortgage Commitment [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	10,074	13,317
Derivative Asset, Fair Value	27	96
Derivative Liability, Fair Value	20	56
Not Designated as Hedging Instrument [Member] \| Mortgage Banking [Member] \| Other Contract [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	25,031	31,907
Derivative Asset, Fair Value	13	28
Derivative Liability, Fair Value	9	4
Not Designated as Hedging Instrument [Member] \| Customer Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	240,080	218,877
Derivative Asset, Fair Value	2,458	2,780
Derivative Liability, Fair Value	2,010	2,584
Not Designated as Hedging Instrument [Member] \| Customer Contracts [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	215,511	196,988
Derivative Asset, Fair Value	2,212	2,438
Derivative Liability, Fair Value	1,766	2,275
Not Designated as Hedging Instrument [Member] \| Customer Contracts [Member] \| Foreign Exchange And Other Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	24,569	21,889
Derivative Asset, Fair Value	246	342
Derivative Liability, Fair Value	244	309
Not Designated as Hedging Instrument [Member] \| Customer Contracts [Member] \| Swap [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	190,003	173,777
Derivative Asset, Fair Value	2,125	2,373
Derivative Liability, Fair Value	1,730	2,214
Not Designated as Hedging Instrument [Member] \| Customer Contracts [Member] \| Future [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	3,670	4,053
Not Designated as Hedging Instrument [Member] \| Customer Contracts [Member] \| Mortgage Commitment [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	2,649	2,955
Derivative Asset, Fair Value	4	10
Derivative Liability, Fair Value	3	8
Not Designated as Hedging Instrument [Member] \| Customer Contracts [Member] \| Other Contract [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	19,189	16,203
Derivative Asset, Fair Value	83	55
Derivative Liability, Fair Value	33	53
Not Designated as Hedging Instrument [Member] \| Other Risk Management Activity [Member] \| Foreign Exchange And Other Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	6,785	5,581
Derivative Asset, Fair Value	10	40
Derivative Liability, Fair Value	$ 313	$ 405

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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Fair value of the gross assets less the offsetting amount of derivative assets.

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No definition available.

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- Definition

The amount of setoff associated with the entity's recognized derivative assets with corresponding derivative liability amounts subject to an enforceable master netting agreement or similar agreement.

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No definition available.

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- Definition

Fair value of the gross liabilities less the amount of offsetting amount of derivative liabilities.

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The amount of setoff associated with the entity's recognized derivative liabilities with corresponding derivative asset amounts subject to an enforceable master netting agreement or similar agreement.

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- Definition

Amount of obligation to return cash collateral under master netting arrangements offset against derivative assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
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Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition

Amount of right to receive cash collateral under master netting arrangements offset against derivative liabilities.

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- Definition

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.

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The increase (decrease) during the period in the carrying value of derivative instruments reported as assets that are due to be disposed of within one year (or the normal operating cycle, if longer).

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The increase (decrease) during the period in the carrying value of derivative instruments reported as liabilities that are due to be disposed of within one year (or the normal operating cycle, if longer).

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