Allowance for Credit Losses - Gross Charge-Offs by Year of Origination (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Allowance for Loan and Lease Losses [Roll Forward]
Year one, current fiscal year charge offs			$ 4	$ 7
Year two, current fiscal year charge offs			9	5
Year three, current fiscal year charge offs			12	6
Year four, current fiscal year charge offs			20	4
Year five, current fiscal year charge offs			10	8
Prior year charge offs			34	20
Revolving loans charge offs			6	4
Total charge offs	$ 49	$ 33	95	54
Commercial: \| Commercial, financial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Year one, current fiscal year charge offs			0	1
Year two, current fiscal year charge offs			9	5
Year three, current fiscal year charge offs			11	6
Year four, current fiscal year charge offs			20	4
Year five, current fiscal year charge offs			1	6
Prior year charge offs			9	10
Revolving loans charge offs			2	1
Total charge offs	24	19	52	33
Commercial: \| Commercial Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Year one, current fiscal year charge offs			0	0
Year two, current fiscal year charge offs			0	0
Year three, current fiscal year charge offs			0	0
Year four, current fiscal year charge offs			0	0
Year five, current fiscal year charge offs			9	2
Prior year charge offs			23	8
Revolving loans charge offs			0	0
Total charge offs	19	8	32	10
Consumer: \| Consumer Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Year one, current fiscal year charge offs			0	0
Year two, current fiscal year charge offs			0	0
Year three, current fiscal year charge offs			0	0
Year four, current fiscal year charge offs			0	0
Year five, current fiscal year charge offs			0	0
Prior year charge offs			1	1
Revolving loans charge offs			0	0
Total charge offs	1	1	1	1
Consumer: \| Credit Card and Other
Allowance for Loan and Lease Losses [Roll Forward]
Year one, current fiscal year charge offs			4	6
Year two, current fiscal year charge offs			0	0
Year three, current fiscal year charge offs			1	0
Year four, current fiscal year charge offs			0	0
Year five, current fiscal year charge offs			0	0
Prior year charge offs			1	1
Revolving loans charge offs			4	3
Total charge offs	$ 5	$ 5	$ 10	$ 10

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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- 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
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-6

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

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- Definition

Amount, excluding accrued interest, of writeoff of financing receivable originated more than five years before current fiscal year. Excludes net investment in lease.

+ References

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- Definition

Amount, excluding accrued interest, of writeoff of revolving financing receivable converted to term loan.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-6A

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Amount, excluding accrued interest, of writeoff of financing receivable originated four years before current fiscal year. Excludes net investment in lease.

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Amount, excluding accrued interest, of writeoff of financing receivable originated three years before current fiscal year. Excludes net investment in lease.

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Amount, excluding accrued interest, of writeoff of financing receivable originated in current fiscal year. Excludes net investment in lease.

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Amount, excluding accrued interest, of writeoff of financing receivable originated two years before current fiscal year. Excludes net investment in lease.

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Amount, excluding accrued interest, of writeoff of financing receivable originated in fiscal year before current fiscal year. Excludes net investment in lease.

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