Financial Derivatives (Total Derivatives) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative, Notional Amount	$ 466,707	$ 443,379
Derivative Asset, Fair Value	6,533	3,502
Derivative Asset, Fair Value Offset Amount	720	690
Derivative Asset, Cash Collateral	1,434	616
Derivative Asset, Net Fair Value	4,379	2,196
Derivative Liability, Fair Value	2,756	2,019
Derivative Liability, Fair Value Offset Amount	720	690
Derivative Liability, Cash Collateral	1,452	790
Derivative Liability, Net Fair Value	584	539
Commodity Contracts
Derivative [Line Items]
Derivative Asset, Fair Value	411	306
Derivative Asset, Cash Collateral	4	18
Derivative Liability, Fair Value	384	301
Derivative Liability, Cash Collateral	103	17
Foreign Exchange And Other Contract
Derivative [Line Items]
Derivative Asset, Fair Value	271	213
Derivative Asset, Cash Collateral	4	5
Derivative Liability, Fair Value	590	425
Derivative Liability, Cash Collateral	170	81
Designated as Hedging Instrument
Derivative [Line Items]
Derivative, Notional Amount	48,103	55,407
Derivative Asset, Fair Value	14	6
Derivative Liability, Fair Value	22	6
Designated as Hedging Instrument \| Fair Value Hedging \| Interest Rate Contract
Derivative [Line Items]
Derivative, Notional Amount	24,153	30,663
Designated as Hedging Instrument \| Cash Flow Hedging \| Interest Rate Contract
Derivative [Line Items]
Derivative, Notional Amount	22,875	23,642
Derivative Asset, Fair Value	14	6
Derivative Liability, Fair Value
Designated as Hedging Instrument \| Net Investment Hedging \| Foreign Exchange Contract
Derivative [Line Items]
Derivative, Notional Amount	1,075	1,102
Derivative Asset, Fair Value
Derivative Liability, Fair Value	22	6
Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative, Notional Amount	418,604	387,972
Derivative Asset, Fair Value	6,519	3,496
Derivative Liability, Fair Value	2,734	2,013
Not Designated as Hedging Instrument \| Mortgage Banking \| Interest Rate Contract
Derivative [Line Items]
Derivative, Notional Amount	66,471	66,366
Derivative Asset, Fair Value	158	93
Derivative Liability, Fair Value	79	67
Not Designated as Hedging Instrument \| Mortgage Banking \| Swap \| Interest Rate Contract
Derivative [Line Items]
Derivative, Notional Amount	50,511	52,007
Derivative Asset, Fair Value		1
Derivative Liability, Fair Value
Not Designated as Hedging Instrument \| Mortgage Banking \| Future \| Interest Rate Contract
Derivative [Line Items]
Derivative, Notional Amount	2,841	3,487
Not Designated as Hedging Instrument \| Mortgage Banking \| Mortgage-backed commitments \| Interest Rate Contract
Derivative [Line Items]
Derivative, Notional Amount	11,288	7,738
Derivative Asset, Fair Value	147	60
Derivative Liability, Fair Value	77	44
Not Designated as Hedging Instrument \| Mortgage Banking \| Other Contract \| Interest Rate Contract
Derivative [Line Items]
Derivative, Notional Amount	1,831	3,134
Derivative Asset, Fair Value	11	32
Derivative Liability, Fair Value	2	23
Not Designated as Hedging Instrument \| Customer-related Contracts
Derivative [Line Items]
Derivative, Notional Amount	341,202	311,405
Derivative Asset, Fair Value	6,357	3,394
Derivative Liability, Fair Value	2,330	1,689
Not Designated as Hedging Instrument \| Customer-related Contracts \| Interest Rate Contract
Derivative [Line Items]
Derivative, Notional Amount	305,663	274,878
Derivative Asset, Fair Value	5,679	2,884
Derivative Liability, Fair Value	1,703	1,226
Not Designated as Hedging Instrument \| Customer-related Contracts \| Commodity Contracts
Derivative [Line Items]
Derivative, Notional Amount	8,919	9,407
Derivative Asset, Fair Value	411	306
Derivative Liability, Fair Value	384	301
Not Designated as Hedging Instrument \| Customer-related Contracts \| Foreign Exchange And Other Contract
Derivative [Line Items]
Derivative, Notional Amount	26,620	27,120
Derivative Asset, Fair Value	267	204
Derivative Liability, Fair Value	243	162
Not Designated as Hedging Instrument \| Customer-related Contracts \| Swap \| Interest Rate Contract
Derivative [Line Items]
Derivative, Notional Amount	280,125	249,075
Derivative Asset, Fair Value	5,475	2,769
Derivative Liability, Fair Value	1,601	1,187
Not Designated as Hedging Instrument \| Customer-related Contracts \| Swap \| Commodity Contracts
Derivative [Line Items]
Derivative, Notional Amount	6,149	5,204
Derivative Asset, Fair Value	350	234
Derivative Liability, Fair Value	323	229
Not Designated as Hedging Instrument \| Customer-related Contracts \| Future \| Interest Rate Contract
Derivative [Line Items]
Derivative, Notional Amount	1,235	703
Not Designated as Hedging Instrument \| Customer-related Contracts \| Mortgage-backed commitments \| Interest Rate Contract
Derivative [Line Items]
Derivative, Notional Amount	4,178	3,721
Derivative Asset, Fair Value	11	2
Derivative Liability, Fair Value	14	6
Not Designated as Hedging Instrument \| Customer-related Contracts \| Other Contract \| Interest Rate Contract
Derivative [Line Items]
Derivative, Notional Amount	20,125	21,379
Derivative Asset, Fair Value	193	113
Derivative Liability, Fair Value	88	33
Not Designated as Hedging Instrument \| Customer-related Contracts \| Other Contract \| Commodity Contracts
Derivative [Line Items]
Derivative, Notional Amount	2,770	4,203
Derivative Asset, Fair Value	61	72
Derivative Liability, Fair Value	61	72
Not Designated as Hedging Instrument \| Other Risk Management Activity \| Foreign Exchange And Other Contract
Derivative [Line Items]
Derivative, Notional Amount	10,931	10,201
Derivative Asset, Fair Value	4	9
Derivative Liability, Fair Value	$ 325	$ 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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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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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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