Loans and ACL - Loans Modified During Period That Were in Payment Default (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2025	Dec. 31, 2024
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	$ 192	$ 161
Renewals
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	24	21
Extended Maturity [Member]
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	13	15
Contractual Interest Rate Adjustments
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	3	2
Capitalizations
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	5	6
Payment Delays
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	98	76
Combination - Capitalization and Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	40	33
Other
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	9	8
Commercial: | Commercial and industrial
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	23	18
Commercial: | Commercial and industrial | Renewals
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	23	18
Commercial: | Commercial and industrial | Extended Maturity [Member]
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Commercial: | Commercial and industrial | Contractual Interest Rate Adjustments
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Commercial: | Commercial and industrial | Capitalizations
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Commercial: | Commercial and industrial | Payment Delays
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Commercial: | Commercial and industrial | Combination - Capitalization and Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Commercial: | Commercial and industrial | Other
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Commercial: | CRE
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	1	3
Commercial: | CRE | Renewals
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	1	3
Commercial: | CRE | Extended Maturity [Member]
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Commercial: | CRE | Contractual Interest Rate Adjustments
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Commercial: | CRE | Capitalizations
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Commercial: | CRE | Payment Delays
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Commercial: | CRE | Combination - Capitalization and Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Commercial: | CRE | Other
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Consumer: | Residential mortgage
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	132	102
Consumer: | Residential mortgage | Renewals
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Consumer: | Residential mortgage | Extended Maturity [Member]
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	11	13
Consumer: | Residential mortgage | Contractual Interest Rate Adjustments
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Consumer: | Residential mortgage | Capitalizations
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	5	6
Consumer: | Residential mortgage | Payment Delays
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	69	44
Consumer: | Residential mortgage | Combination - Capitalization and Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	40	33
Consumer: | Residential mortgage | Other
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	7	6
Consumer: | Indirect auto
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	32	35
Consumer: | Indirect auto | Renewals
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Consumer: | Indirect auto | Extended Maturity [Member]
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	1	1
Consumer: | Indirect auto | Contractual Interest Rate Adjustments
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Consumer: | Indirect auto | Capitalizations
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Consumer: | Indirect auto | Payment Delays
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	29	32
Consumer: | Indirect auto | Combination - Capitalization and Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Consumer: | Indirect auto | Other
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	2	2
Consumer: | Other consumer
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	1	1
Consumer: | Other consumer | Renewals
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Consumer: | Other consumer | Extended Maturity [Member]
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	1	1
Consumer: | Other consumer | Contractual Interest Rate Adjustments
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Consumer: | Other consumer | Capitalizations
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Consumer: | Other consumer | Payment Delays
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Consumer: | Other consumer | Combination - Capitalization and Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Consumer: | Other consumer | Other
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Credit card
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	3	2
Credit card | Renewals
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Credit card | Extended Maturity [Member]
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Credit card | Contractual Interest Rate Adjustments
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	3	2
Credit card | Capitalizations
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Credit card | Payment Delays
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Credit card | Combination - Capitalization and Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	0	0
Credit card | Other
Financing Receivable, Modified, Subsequent Default [Line Items]
Modifications Made in the Current Period That Were in Payment Default	$ 0	$ 0