Allowance for Credit Losses - Gross Charge-Offs by Year of Origination (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Allowance for Loan and Lease Losses [Roll Forward]
Year one, current fiscal year charge offs			$ 6	$ 83
Year two, current fiscal year charge offs			15	13
Year three, current fiscal year charge offs			15	7
Year four, current fiscal year charge offs			23	5
Year five, current fiscal year charge offs			17	11
Prior year charge offs			43	30
Revolving loans charge offs			9	10
Total charge offs	$ 33	$ 104	128	159
Commercial: \| Commercial, financial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Year one, current fiscal year charge offs			0	74
Year two, current fiscal year charge offs			13	13
Year three, current fiscal year charge offs			13	6
Year four, current fiscal year charge offs			23	4
Year five, current fiscal year charge offs			1	9
Prior year charge offs			11	13
Revolving loans charge offs			3	5
Total charge offs	12	91	64	124
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			1	0
Year four, current fiscal year charge offs			0	0
Year five, current fiscal year charge offs			16	2
Prior year charge offs			30	13
Revolving loans charge offs			0	0
Total charge offs	15	5	47	15
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			1	0
Year three, current fiscal year charge offs			0	0
Year four, current fiscal year charge offs			0	1
Year five, current fiscal year charge offs			0	0
Prior year charge offs			1	2
Revolving loans charge offs			0	0
Total charge offs	1	1	2	3
Consumer: \| Credit Card and Other
Allowance for Loan and Lease Losses [Roll Forward]
Year one, current fiscal year charge offs			6	9
Year two, current fiscal year charge offs			1	0
Year three, current fiscal year charge offs			1	1
Year four, current fiscal year charge offs			0	0
Year five, current fiscal year charge offs			0	0
Prior year charge offs			1	2
Revolving loans charge offs			6	5
Total charge offs	$ 5	$ 7	$ 15	$ 17

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 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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