Financial Derivatives (Total Derivatives) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative, Notional Amount	$ 473,540	$ 443,379
Derivative Asset, Fair Value	7,343	3,502
Derivative Liability, Fair Value	2,710	2,019
Derivative Asset, Fair Value Offset Amount	864	690
Derivative Liability, Fair Value Offset Amount	864	690
Derivative Asset, Cash Collateral	1,699	616
Derivative Liability, Cash Collateral	1,308	790
Derivative Asset, Net Fair Value	4,780	2,196
Derivative Liability, Net Fair Value	538	539
Commodity Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value	497	306
Derivative Liability, Fair Value	475	301
Derivative Asset, Cash Collateral	14	18
Derivative Liability, Cash Collateral	59	17
Foreign Exchange And Other Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value	281	213
Derivative Liability, Fair Value	337	425
Derivative Asset, Cash Collateral	12	5
Derivative Liability, Cash Collateral	90	81
Designated as Hedging Instruments under GAAP [Member]
Derivative [Line Items]
Derivative, Notional Amount	48,396	55,407
Derivative Asset, Fair Value	42	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	27,007	30,663
Designated as Hedging Instruments under GAAP [Member] \| Cash Flow Hedging [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	20,229	23,642
Derivative Asset, Fair Value	9	6
Designated as Hedging Instruments under GAAP [Member] \| Net Investment Hedging [Member] \| Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount	1,160	1,102
Derivative Asset, Fair Value	33
Derivative Liability, Fair Value		6
Not Designated as Hedging Instrument under GAAP [Member]
Derivative [Line Items]
Derivative, Notional Amount	425,144	387,972
Derivative Asset, Fair Value	7,301	3,496
Derivative Liability, Fair Value	2,710	2,013
Not Designated as Hedging Instrument under GAAP [Member] \| Mortgage Banking [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	74,905	66,366
Derivative Asset, Fair Value	146	93
Derivative Liability, Fair Value	87	67
Not Designated as Hedging Instrument under GAAP [Member] \| Mortgage Banking [Member] \| Swap [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	55,056	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	2,809	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	13,460	7,738
Derivative Asset, Fair Value	139	60
Derivative Liability, Fair Value	82	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	3,580	3,134
Derivative Asset, Fair Value	7	32
Derivative Liability, Fair Value	5	23
Not Designated as Hedging Instrument under GAAP [Member] \| Customer Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	340,132	311,405
Derivative Asset, Fair Value	7,118	3,394
Derivative Liability, Fair Value	2,494	1,689
Not Designated as Hedging Instrument under GAAP [Member] \| Customer Contracts [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	306,480	274,878
Derivative Asset, Fair Value	6,410	2,884
Derivative Liability, Fair Value	1,811	1,226
Not Designated as Hedging Instrument under GAAP [Member] \| Customer Contracts [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount	8,608	9,407
Derivative Asset, Fair Value	497	306
Derivative Liability, Fair Value	475	301
Not Designated as Hedging Instrument under GAAP [Member] \| Customer Contracts [Member] \| Foreign Exchange And Other Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount	25,044	27,120
Derivative Asset, Fair Value	211	204
Derivative Liability, Fair Value	208	162
Not Designated as Hedging Instrument under GAAP [Member] \| Customer Contracts [Member] \| Swap [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	278,984	249,075
Derivative Asset, Fair Value	6,167	2,769
Derivative Liability, Fair Value	1,717	1,187
Not Designated as Hedging Instrument under GAAP [Member] \| Customer Contracts [Member] \| Swap [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount	5,566	5,204
Derivative Asset, Fair Value	397	234
Derivative Liability, Fair Value	375	229
Not Designated as Hedging Instrument under GAAP [Member] \| Customer Contracts [Member] \| Future [Member] \| Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	1,252	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	4,187	3,721
Derivative Asset, Fair Value	12	2
Derivative Liability, Fair Value	11	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	22,057	21,379
Derivative Asset, Fair Value	231	113
Derivative Liability, Fair Value	83	33
Not Designated as Hedging Instrument under GAAP [Member] \| Customer Contracts [Member] \| Other Contract [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount	3,042	4,203
Derivative Asset, Fair Value	100	72
Derivative Liability, Fair Value	100	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	10,107	10,201
Derivative Asset, Fair Value	37	9
Derivative Liability, Fair Value	$ 129	$ 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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