Financial Derivatives (Total Derivatives) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative, Notional Amount	$ 488,492	$ 443,379
Derivative Asset, Fair Value	8,773	3,502
Derivative Liability, Fair Value	3,928	2,019
Derivative Asset, Fair Value Offset Amount	1,341	690
Derivative Liability, Fair Value Offset Amount	1,341	690
Derivative Asset, Cash Collateral	2,110	616
Derivative Liability, Cash Collateral	1,109	790
Derivative Asset, Net Fair Value	5,322	2,196
Derivative Liability, Net Fair Value	1,478	539
Commodity Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value	1,044	306
Derivative Liability, Fair Value	1,035	301
Derivative Asset, Cash Collateral	382	18
Derivative Liability, Cash Collateral	22	17
Foreign Exchange And Other Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value	624	213
Derivative Liability, Fair Value	627	425
Derivative Asset, Cash Collateral	27	5
Derivative Liability, Cash Collateral	117	81
Designated as Hedging Instruments under GAAP [Member]
Derivative [Line Items]
Derivative, Notional Amount	57,835	55,407
Derivative Asset, Fair Value	203	6
Derivative Liability, Fair Value		6
Designated as Hedging Instruments under GAAP [Member] \| Fair Value Hedging [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	31,764	30,663
Designated as Hedging Instruments under GAAP [Member] \| Cash Flow Hedging [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	24,889	23,642
Derivative Asset, Fair Value	133	6
Designated as Hedging Instruments under GAAP [Member] \| Net Investment Hedging [Member] \| Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount	1,182	1,102
Derivative Asset, Fair Value	70
Derivative Liability, Fair Value		6
Not Designated as Hedging Instrument under GAAP [Member]
Derivative [Line Items]
Derivative, Notional Amount	430,657	387,972
Derivative Asset, Fair Value	8,570	3,496
Derivative Liability, Fair Value	3,928	2,013
Not Designated as Hedging Instrument under GAAP [Member] \| Mortgage Banking [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	83,120	66,366
Derivative Asset, Fair Value	283	93
Derivative Liability, Fair Value	255	67
Not Designated as Hedging Instrument under GAAP [Member] \| Mortgage Banking [Member] \| Swap [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	54,029	52,007
Derivative Asset, Fair Value		1
Not Designated as Hedging Instrument under GAAP [Member] \| Mortgage Banking [Member] \| Future [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	2,901	3,487
Not Designated as Hedging Instrument under GAAP [Member] \| Mortgage Banking [Member] \| Mortgage Commitment [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	19,022	7,738
Derivative Asset, Fair Value	248	60
Derivative Liability, Fair Value	206	44
Not Designated as Hedging Instrument under GAAP [Member] \| Mortgage Banking [Member] \| Other Contract [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	7,168	3,134
Derivative Asset, Fair Value	35	32
Derivative Liability, Fair Value	49	23
Not Designated as Hedging Instrument under GAAP [Member] \| Customer Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	337,050	311,405
Derivative Asset, Fair Value	8,146	3,394
Derivative Liability, Fair Value	3,482	1,689
Not Designated as Hedging Instrument under GAAP [Member] \| Customer Contracts [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	300,766	274,878
Derivative Asset, Fair Value	6,689	2,884
Derivative Liability, Fair Value	2,011	1,226
Not Designated as Hedging Instrument under GAAP [Member] \| Customer Contracts [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount	9,185	9,407
Derivative Asset, Fair Value	1,044	306
Derivative Liability, Fair Value	1,035	301
Not Designated as Hedging Instrument under GAAP [Member] \| Customer Contracts [Member] \| Foreign Exchange And Other Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount	27,099	27,120
Derivative Asset, Fair Value	413	204
Derivative Liability, Fair Value	436	162
Not Designated as Hedging Instrument under GAAP [Member] \| Customer Contracts [Member] \| Swap [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	268,654	249,075
Derivative Asset, Fair Value	6,346	2,769
Derivative Liability, Fair Value	1,834	1,187
Not Designated as Hedging Instrument under GAAP [Member] \| Customer Contracts [Member] \| Swap [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount	5,152	5,204
Derivative Asset, Fair Value	792	234
Derivative Liability, Fair Value	783	229
Not Designated as Hedging Instrument under GAAP [Member] \| Customer Contracts [Member] \| Future [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	1,491	703
Not Designated as Hedging Instrument under GAAP [Member] \| Customer Contracts [Member] \| Mortgage Commitment [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	7,182	3,721
Derivative Asset, Fair Value	44	2
Derivative Liability, Fair Value	71	6
Not Designated as Hedging Instrument under GAAP [Member] \| Customer Contracts [Member] \| Other Contract [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	23,439	21,379
Derivative Asset, Fair Value	299	113
Derivative Liability, Fair Value	106	33
Not Designated as Hedging Instrument under GAAP [Member] \| Customer Contracts [Member] \| Other Contract [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount	4,033	4,203
Derivative Asset, Fair Value	252	72
Derivative Liability, Fair Value	252	72
Not Designated as Hedging Instrument under GAAP [Member] \| Other Risk Management Activity [Member] \| Foreign Exchange And Other Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount	10,487	10,201
Derivative Asset, Fair Value	141	9
Derivative Liability, Fair Value	$ 191	$ 257

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

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

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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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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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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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