Allowance for Credit Losses - Rollforward of Allowance for Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 622	$ 914	$ 670	$ 963
Charge-offs	(21)	(6)	(40)	(29)
Recoveries	9	16	18	31
Ending balance	624	815	624	815
Loans and leases	56,529		56,529		$ 54,859
Funded And Unfunded Loan Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Ending balance	704	890	704	890
Funded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan and lease losses	14	(109)	(24)	(150)
Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	64	81	66	85
Provision for loan and lease losses	16	(6)	14	(10)
Ending balance	80	75	80	75
Commercial \| Commercial, financial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	287	442	334	453
Charge-offs	(12)	(2)	(25)	(16)
Recoveries	1	5	4	11
Ending balance	274	385	274	385
Loans and leases	31,276		31,276		31,068
Commercial \| Commercial, financial and industrial \| Paycheck Protection Plan
Allowance for Loan and Lease Losses [Roll Forward]
Loans and leases	375	3,800	375	3,800	1,000
Commercial \| Commercial, financial and industrial \| Funded And Unfunded Loan Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Ending balance	327	442	327	442
Commercial \| Commercial, financial and industrial \| Funded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan and lease losses	(2)	(60)	(39)	(63)
Commercial \| Commercial, financial and industrial \| Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	43	62	46	65
Provision for loan and lease losses	10	(5)	7	(8)
Ending balance	53	57	53	57
Commercial \| Commercial Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	151	232	154	242
Charge-offs	0	0	0	(3)
Recoveries	1	1	1	3
Ending balance	141	210	141	210
Loans and leases	12,942		12,942		12,109
Commercial \| Commercial Real Estate \| Funded And Unfunded Loan Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Ending balance	158	219	158	219
Commercial \| Commercial Real Estate \| Funded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan and lease losses	(11)	(23)	(14)	(32)
Commercial \| Commercial Real Estate \| Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	12	11	12	10
Provision for loan and lease losses	5	(2)	5	(1)
Ending balance	17	9	17	9
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Loans and leases	11,441		11,441		10,772
Consumer \| Consumer Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	164	222	163	242
Charge-offs	(2)	(1)	(3)	(4)
Recoveries	6	8	11	14
Ending balance	183	203	183	203
Loans and leases	11,441		11,441		10,772
Consumer \| Consumer Real Estate \| Funded And Unfunded Loan Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Ending balance	193	212	193	212
Consumer \| Consumer Real Estate \| Funded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan and lease losses	15	(26)	12	(49)
Consumer \| Consumer Real Estate \| Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	9	8	8	10
Provision for loan and lease losses	1	1	2	(1)
Ending balance	10	9	10	9
Consumer \| Credit Card and Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	20	18	19	26
Charge-offs	(7)	(3)	(12)	(6)
Recoveries	1	2	2	3
Ending balance	26	17	26	17
Loans and leases	870		870		$ 910
Consumer \| Credit Card and Other \| Funded And Unfunded Loan Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Ending balance	26	17	26	17
Consumer \| Credit Card and Other \| Funded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan and lease losses	12	0	17	(6)
Consumer \| Credit Card and Other \| Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	0	0	0	0
Provision for loan and lease losses	0	0	0	0
Ending balance	$ 0	$ 0	$ 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. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446

+ Details

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- Definition

Amount, excluding accrued interest, of increase in allowance for credit loss on financing receivable from recovery. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (e)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

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- Definition

Amount, excluding accrued interest, of decrease in allowance for credit loss on financing receivable from writeoff. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

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- Definition

Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919230-210447

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 3B
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL120267963-210447

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- Definition

Amount, excluding accrued interest, of credit loss expense (reversal of expense) on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

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