Loans and Related Allowance for Credit Losses (Rollforward of Allowance for Credit Losses) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 2,742	$ 2,629	$ 2,611
Charge-offs	(1,192)	(974)	(764)
Recoveries	360	332	344
Net (charge-offs)	(832)	(642)	(420)
Provision for credit losses	2,985	773	408
Net (increase) / decrease in allowance for unfunded loan commitments and letters of credit		(33)	12
Other	3	15	18
Ending balance	5,361	2,742	2,629
Loans collectively evaluated for impairment - associated allowance		2,277	2,145
Loans collectively evaluated for impairment		235,498	221,363
Fair value option loans		742	782
Purchased impaired loans		1,719	2,017
Total Loans	241,928	239,843	226,245
Allowance For Unfunded Lending Related Commitments [Roll Forward]
Beginning balance	318
Provision for (recapture of) credit losses	87
Ending balance	584	318
Allowance for credit loss and off-balance sheet liability	5,945
Allowances for investment securities and other financial assets	109
TDRs
Allowance for Loan and Lease Losses [Roll Forward]
Loans individually evaluated for impairment - associated allowance		133	161
Loans individually evaluated for impairment		1,664	1,851
Other Loans
Allowance for Loan and Lease Losses [Roll Forward]
Loans individually evaluated for impairment - associated allowance		58	48
Loans individually evaluated for impairment		220	232
Purchased Impaired Loans
Allowance for Loan and Lease Losses [Roll Forward]
Impaired loans - associated allowance		274	275
Cumulative Effect, Period of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	463
Ending balance		463
Allowance For Unfunded Lending Related Commitments [Roll Forward]
Beginning balance	179
Ending balance		179
Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	3,205
Ending balance		3,205
Allowance For Unfunded Lending Related Commitments [Roll Forward]
Beginning balance	497
Ending balance		497
Allowance for credit loss and off-balance sheet liability	5,945	3,702
Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,812	1,663	1,582
Charge-offs	(407)	(216)	(124)
Recoveries	94	78	99
Net (charge-offs)	(313)	(138)	(25)
Provision for credit losses	2,139	320	97
Net (increase) / decrease in allowance for unfunded loan commitments and letters of credit		(34)	11
Other	3	1	(2)
Ending balance	3,337	1,812	1,663
Loans collectively evaluated for impairment - associated allowance		1,714	1,590
Loans collectively evaluated for impairment		160,021	151,641
Purchased impaired loans
Total Loans	167,203	160,602	152,282
Allowance For Unfunded Lending Related Commitments [Roll Forward]
Beginning balance	316
Provision for (recapture of) credit losses	116
Ending balance	485	316
Allowance for credit loss and off-balance sheet liability	3,822
Commercial \| TDRs
Allowance for Loan and Lease Losses [Roll Forward]
Loans individually evaluated for impairment - associated allowance		40	25
Loans individually evaluated for impairment		361	409
Commercial \| Other Loans
Allowance for Loan and Lease Losses [Roll Forward]
Loans individually evaluated for impairment - associated allowance		58	48
Loans individually evaluated for impairment		220	232
Commercial \| Purchased Impaired Loans
Allowance for Loan and Lease Losses [Roll Forward]
Impaired loans - associated allowance
Commercial \| Cumulative Effect, Period of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	(304)
Ending balance		(304)
Allowance For Unfunded Lending Related Commitments [Roll Forward]
Beginning balance	53
Ending balance		53
Commercial \| Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,508
Ending balance		1,508
Allowance For Unfunded Lending Related Commitments [Roll Forward]
Beginning balance	369
Ending balance		369
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	930	966	1,029
Charge-offs	(785)	(758)	(640)
Recoveries	266	254	245
Net (charge-offs)	(519)	(504)	(395)
Provision for credit losses	846	453	311
Net (increase) / decrease in allowance for unfunded loan commitments and letters of credit		1	1
Other		14	20
Ending balance	2,024	930	966
Loans collectively evaluated for impairment - associated allowance		563	555
Loans collectively evaluated for impairment		75,477	69,722
Fair value option loans		742	782
Purchased impaired loans		1,719	2,017
Total Loans	74,725	79,241	73,963
Allowance For Unfunded Lending Related Commitments [Roll Forward]
Beginning balance	2
Provision for (recapture of) credit losses	(29)
Ending balance	99	2
Allowance for credit loss and off-balance sheet liability	2,123
Consumer \| TDRs
Allowance for Loan and Lease Losses [Roll Forward]
Loans individually evaluated for impairment - associated allowance		93	136
Loans individually evaluated for impairment		1,303	1,442
Consumer \| Purchased Impaired Loans
Allowance for Loan and Lease Losses [Roll Forward]
Impaired loans - associated allowance		274	$ 275
Consumer \| Cumulative Effect, Period of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	767
Ending balance		767
Allowance For Unfunded Lending Related Commitments [Roll Forward]
Beginning balance	126
Ending balance		126
Consumer \| Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,697
Ending balance		1,697
Allowance For Unfunded Lending Related Commitments [Roll Forward]
Beginning balance	$ 128
Ending balance		$ 128

Allowance For Unfunded Lending Related Commitments

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Debt Securities, Available-For-Sale And Held-To-Maturity, And Other Financial Assets, Allowance for Credit Loss

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No definition available.

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Represents loans accounted for under the fair value option and included in the loan portfolio that are not evaluated for impairment because they are accounted for at fair value. There is no allowance recorded on these loans.

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Total allowance for credit losses related to loans, including the allowance for loan and lease losses and alowance for unfunded lending related commitments

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Financing Receivable, Allowance for Credit Loss, Other Increase (Decrease)

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Net change in allowance for unfunded loan commitments and letters of credit which is included in the provision for credit losses.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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The recorded balance, net of any applicable reductions (for example, unamortized accretable yield and allowance for loan losses). This relates to loans not accounted for debt securities with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

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Amount, after recovery, of writeoff of financing receivable, charged against allowance for credit loss.

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Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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Amount of increase in allowance for credit loss on financing receivable from recovery.

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Amount of writeoff of financing receivable, charged against allowance for credit loss.

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The balance of financing receivables that were collectively evaluated for impairment.

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The balance of financing receivables that were individually evaluated for impairment.

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Amount of allowance for credit losses related to recorded investment.

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Amount, before allowance for credit loss, of financing receivable.

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Amount of expected credit loss for credit exposure on off-balance-sheet commitment, including but not limited to, loan commitment, standby letter of credit, financial guarantee not accounted for as insurance. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

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Amount of expense (reversal of expense) for expected credit loss for off-balance sheet credit exposure. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

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Amount of credit loss expense (reversal of expense) for financing receivable.

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