Allowance for Credit Losses - Rollforward of Allowance for Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 670	$ 963
Charge-offs	(19)	(23)
Recoveries	9	15
Provision for credit losses	(40)	(45)
Ending balance	622	914
Loans and leases	55,012		$ 54,859
Funded And Unfunded Loan Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Ending balance	686	995
Funded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for credit losses	(38)	(41)
Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	66	85
Provision for credit losses	(2)	(4)
Ending balance	64	81
Commercial \| Commercial, financial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	334	453
Charge-offs	(13)	(16)
Recoveries	3	6
Ending balance	287	442
Loans and leases	30,798		31,068
Commercial \| Commercial, financial and industrial \| Paycheck Protection Plan
Allowance for Loan and Lease Losses [Roll Forward]
Loans and leases	642	5,100	1,000
Commercial \| Commercial, financial and industrial \| Funded And Unfunded Loan Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Ending balance	330	504
Commercial \| Commercial, financial and industrial \| Funded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for credit losses	(37)	(1)
Commercial \| Commercial, financial and industrial \| Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	46	65
Provision for credit losses	(3)	(3)
Ending balance	43	62
Commercial \| Commercial Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	154	242
Charge-offs	0	(3)
Recoveries	0	2
Ending balance	151	232
Loans and leases	12,487		12,109
Commercial \| Commercial Real Estate \| Funded And Unfunded Loan Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Ending balance	163	243
Commercial \| Commercial Real Estate \| Funded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for credit losses	(3)	(9)
Commercial \| Commercial Real Estate \| Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	12	10
Provision for credit losses	0	1
Ending balance	12	11
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Loans and leases	10,874		10,772
Consumer \| Consumer Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	163	242
Charge-offs	(1)	(1)
Recoveries	5	6
Ending balance	164	222
Loans and leases	10,874		10,772
Consumer \| Consumer Real Estate \| Funded And Unfunded Loan Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Ending balance	173	230
Consumer \| Consumer Real Estate \| Funded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for credit losses	(3)	(25)
Consumer \| Consumer Real Estate \| Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	8	10
Provision for credit losses	1	(2)
Ending balance	9	8
Consumer \| Credit Card and Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	19	26
Charge-offs	(5)	(3)
Recoveries	1	1
Ending balance	20	18
Loans and leases	853		$ 910
Consumer \| Credit Card and Other \| Funded And Unfunded Loan Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Ending balance	20	18
Consumer \| Credit Card and Other \| Funded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for credit losses	5	(6)
Consumer \| Credit Card and Other \| Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	0	0
Provision for credit losses	0	0
Ending balance	$ 0	$ 0

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

No definition available.

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- Definition

Amount excluding accrued interest, of allowance for credit loss on financing receivable.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446

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- Definition

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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Amount excluding accrued interest, before allowance for credit loss, of financing receivable.

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

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